package net

import "net"

Package net provides a portable interface for network I/O, including TCP/IP, UDP, domain name resolution, and Unix domain sockets.

Although the package provides access to low-level networking primitives, most clients will need only the basic interface provided by the Dial, Listen, and Accept functions and the associated Conn and Listener interfaces. The crypto/tls package uses the same interfaces and similar Dial and Listen functions.

The Dial function connects to a server: 

conn, err := net.Dial("tcp", "golang.org:80")
if err != nil {
	// handle error
}
fmt.Fprintf(conn, "GET / HTTP/1.0\r\n\r\n")
status, err := bufio.NewReader(conn).ReadString('\n')
// ...

The Listen function creates servers: 

ln, err := net.Listen("tcp", ":8080")
if err != nil {
	// handle error
}
for {
	conn, err := ln.Accept()
	if err != nil {
		// handle error
	}
	go handleConnection(conn)
}

Name Resolution

The method for resolving domain names, whether indirectly with functions like Dial or directly with functions like LookupHost and LookupAddr, varies by operating system.

On Unix systems, the resolver has two options for resolving names. It can use a pure Go resolver that sends DNS requests directly to the servers listed in /etc/resolv.conf, or it can use a cgo-based resolver that calls C library routines such as getaddrinfo and getnameinfo.

By default the pure Go resolver is used, because a blocked DNS request consumes only a goroutine, while a blocked C call consumes an operating system thread. When cgo is available, the cgo-based resolver is used instead under a variety of conditions: on systems that do not let programs make direct DNS requests (OS X), when the LOCALDOMAIN environment variable is present (even if empty), when the RES_OPTIONS or HOSTALIASES environment variable is non-empty, when the ASR_CONFIG environment variable is non-empty (OpenBSD only), when /etc/resolv.conf or /etc/nsswitch.conf specify the use of features that the Go resolver does not implement, and when the name being looked up ends in .local or is an mDNS name.

The resolver decision can be overridden by setting the netdns value of the GODEBUG environment variable (see package runtime) to go or cgo, as in: 

export GODEBUG=netdns=go    # force pure Go resolver
export GODEBUG=netdns=cgo   # force native resolver (cgo, win32)

The decision can also be forced while building the Go source tree by setting the netgo or netcgo build tag.

A numeric netdns setting, as in GODEBUG=netdns=1, causes the resolver to print debugging information about its decisions. To force a particular resolver while also printing debugging information, join the two settings by a plus sign, as in GODEBUG=netdns=go+1.

On macOS, if Go code that uses the net package is built with -buildmode=c-archive, linking the resulting archive into a C program requires passing -lresolv when linking the C code.

On Plan 9, the resolver always accesses /net/cs and /net/dns.

On Windows, in Go 1.18.x and earlier, the resolver always used C library functions, such as GetAddrInfo and DnsQuery.

Index

Examples

Constants

const (
	IPv4len = 4
	IPv6len = 16
)

IP address lengths (bytes).

Variables

var (
	IPv4bcast     = IPv4(255, 255, 255, 255) // limited broadcast
	IPv4allsys    = IPv4(224, 0, 0, 1)       // all systems
	IPv4allrouter = IPv4(224, 0, 0, 2)       // all routers
	IPv4zero      = IPv4(0, 0, 0, 0)         // all zeros
)

Well-known IPv4 addresses 

var (
	IPv6zero                   = IP{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
	IPv6unspecified            = IP{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
	IPv6loopback               = IP{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1}
	IPv6interfacelocalallnodes = IP{0xff, 0x01, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x01}
	IPv6linklocalallnodes      = IP{0xff, 0x02, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x01}
	IPv6linklocalallrouters    = IP{0xff, 0x02, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x02}
)

Well-known IPv6 addresses 

var DefaultResolver = &Resolver{}

DefaultResolver is the resolver used by the package-level Lookup functions and by Dialers without a specified Resolver. 

var ErrClosed error = errClosed

ErrClosed is the error returned by an I/O call on a network connection that has already been closed, or that is closed by another goroutine before the I/O is completed. This may be wrapped in another error, and should normally be tested using errors.Is(err, net.ErrClosed). 

var (
	ErrWriteToConnected = errors.New("use of WriteTo with pre-connected connection")
)

Various errors contained in OpError.

Functions

func JoinHostPort

func JoinHostPort(host, port string) string

JoinHostPort combines host and port into a network address of the form "host:port". If host contains a colon, as found in literal IPv6 addresses, then JoinHostPort returns "[host]:port".

See func Dial for a description of the host and port parameters.

func LookupAddr

func LookupAddr(addr string) (names []string, err error)

LookupAddr performs a reverse lookup for the given address, returning a list of names mapping to that address.

The returned names are validated to be properly formatted presentation-format domain names. If the response contains invalid names, those records are filtered out and an error will be returned alongside the remaining results, if any.

When using the host C library resolver, at most one result will be returned. To bypass the host resolver, use a custom Resolver.

LookupAddr uses context.Background internally; to specify the context, use Resolver.LookupAddr.

func LookupCNAME

func LookupCNAME(host string) (cname string, err error)

LookupCNAME returns the canonical name for the given host. Callers that do not care about the canonical name can call LookupHost or LookupIP directly; both take care of resolving the canonical name as part of the lookup.

A canonical name is the final name after following zero or more CNAME records. LookupCNAME does not return an error if host does not contain DNS "CNAME" records, as long as host resolves to address records.

The returned canonical name is validated to be a properly formatted presentation-format domain name.

LookupCNAME uses context.Background internally; to specify the context, use Resolver.LookupCNAME.

func LookupHost

func LookupHost(host string) (addrs []string, err error)

LookupHost looks up the given host using the local resolver. It returns a slice of that host's addresses.

LookupHost uses context.Background internally; to specify the context, use Resolver.LookupHost.

func LookupPort

func LookupPort(network, service string) (port int, err error)

LookupPort looks up the port for the given network and service.

LookupPort uses context.Background internally; to specify the context, use Resolver.LookupPort.

func LookupTXT

func LookupTXT(name string) ([]string, error)

LookupTXT returns the DNS TXT records for the given domain name.

LookupTXT uses context.Background internally; to specify the context, use Resolver.LookupTXT.

func ParseCIDR

func ParseCIDR(s string) (IP, *IPNet, error)

ParseCIDR parses s as a CIDR notation IP address and prefix length, like "192.0.2.0/24" or "2001:db8::/32", as defined in RFC 4632 and RFC 4291.

It returns the IP address and the network implied by the IP and prefix length. For example, ParseCIDR("192.0.2.1/24") returns the IP address 192.0.2.1 and the network 192.0.2.0/24.

Example 
package main

import (
	"fmt"
	"log"
	"net"
)

func main() {
	ipv4Addr, ipv4Net, err := net.ParseCIDR("192.0.2.1/24")
	if err != nil {
		log.Fatal(err)
	}
	fmt.Println(ipv4Addr)
	fmt.Println(ipv4Net)

	ipv6Addr, ipv6Net, err := net.ParseCIDR("2001:db8:a0b:12f0::1/32")
	if err != nil {
		log.Fatal(err)
	}
	fmt.Println(ipv6Addr)
	fmt.Println(ipv6Net)

}

Output:

192.0.2.1
192.0.2.0/24
2001:db8:a0b:12f0::1
2001:db8::/32

func Pipe

func Pipe() (Conn, Conn)

Pipe creates a synchronous, in-memory, full duplex network connection; both ends implement the Conn interface. Reads on one end are matched with writes on the other, copying data directly between the two; there is no internal buffering.

func SplitHostPort

func SplitHostPort(hostport string) (host, port string, err error)

SplitHostPort splits a network address of the form "host:port", "host%zone:port", "[host]:port" or "[host%zone]:port" into host or host%zone and port.

A literal IPv6 address in hostport must be enclosed in square brackets, as in "[::1]:80", "[::1%lo0]:80".

See func Dial for a description of the hostport parameter, and host and port results.

Types

type Addr

type Addr interface {
	Network() string // name of the network (for example, "tcp", "udp")
	String() string  // string form of address (for example, "192.0.2.1:25", "[2001:db8::1]:80")
}

Addr represents a network end point address.

The two methods [Addr.Network] and [Addr.String] conventionally return strings that can be passed as the arguments to Dial, but the exact form and meaning of the strings is up to the implementation.

func InterfaceAddrs

func InterfaceAddrs() ([]Addr, error)

InterfaceAddrs returns a list of the system's unicast interface addresses.

The returned list does not identify the associated interface; use Interfaces and Interface.Addrs for more detail.

type AddrError

type AddrError struct {
	Err  string
	Addr string
}

func (*AddrError) Error

func (e *AddrError) Error() string

func (*AddrError) Temporary

func (e *AddrError) Temporary() bool

func (*AddrError) Timeout

func (e *AddrError) Timeout() bool

type Buffers

type Buffers [][]byte

Buffers contains zero or more runs of bytes to write.

On certain machines, for certain types of connections, this is optimized into an OS-specific batch write operation (such as "writev").

func (*Buffers) Read

func (v *Buffers) Read(p []byte) (n int, err error)

Read from the buffers.

Read implements io.Reader for Buffers.

Read modifies the slice v as well as v[i] for 0 <= i < len(v), but does not modify v[i][j] for any i, j.

func (*Buffers) WriteTo

func (v *Buffers) WriteTo(w io.Writer) (n int64, err error)

WriteTo writes contents of the buffers to w.

WriteTo implements io.WriterTo for Buffers.

WriteTo modifies the slice v as well as v[i] for 0 <= i < len(v), but does not modify v[i][j] for any i, j.

type Conn

type Conn interface {
	// Read reads data from the connection.
	// Read can be made to time out and return an error after a fixed
	// time limit; see SetDeadline and SetReadDeadline.
	Read(b []byte) (n int, err error)

	// Write writes data to the connection.
	// Write can be made to time out and return an error after a fixed
	// time limit; see SetDeadline and SetWriteDeadline.
	Write(b []byte) (n int, err error)

	// Close closes the connection.
	// Any blocked Read or Write operations will be unblocked and return errors.
	Close() error

	// LocalAddr returns the local network address, if known.
	LocalAddr() Addr

	// RemoteAddr returns the remote network address, if known.
	RemoteAddr() Addr

	// SetDeadline sets the read and write deadlines associated
	// with the connection. It is equivalent to calling both
	// SetReadDeadline and SetWriteDeadline.
	//
	// A deadline is an absolute time after which I/O operations
	// fail instead of blocking. The deadline applies to all future
	// and pending I/O, not just the immediately following call to
	// Read or Write. After a deadline has been exceeded, the
	// connection can be refreshed by setting a deadline in the future.
	//
	// If the deadline is exceeded a call to Read or Write or to other
	// I/O methods will return an error that wraps os.ErrDeadlineExceeded.
	// This can be tested using errors.Is(err, os.ErrDeadlineExceeded).
	// The error's Timeout method will return true, but note that there
	// are other possible errors for which the Timeout method will
	// return true even if the deadline has not been exceeded.
	//
	// An idle timeout can be implemented by repeatedly extending
	// the deadline after successful Read or Write calls.
	//
	// A zero value for t means I/O operations will not time out.
	SetDeadline(t time.Time) error

	// SetReadDeadline sets the deadline for future Read calls
	// and any currently-blocked Read call.
	// A zero value for t means Read will not time out.
	SetReadDeadline(t time.Time) error

	// SetWriteDeadline sets the deadline for future Write calls
	// and any currently-blocked Write call.
	// Even if write times out, it may return n > 0, indicating that
	// some of the data was successfully written.
	// A zero value for t means Write will not time out.
	SetWriteDeadline(t time.Time) error
}

Conn is a generic stream-oriented network connection.

Multiple goroutines may invoke methods on a Conn simultaneously.

func Dial

func Dial(network, address string) (Conn, error)

Dial connects to the address on the named network.

Known networks are "tcp", "tcp4" (IPv4-only), "tcp6" (IPv6-only), "udp", "udp4" (IPv4-only), "udp6" (IPv6-only), "ip", "ip4" (IPv4-only), "ip6" (IPv6-only), "unix", "unixgram" and "unixpacket".

For TCP and UDP networks, the address has the form "host:port". The host must be a literal IP address, or a host name that can be resolved to IP addresses. The port must be a literal port number or a service name. If the host is a literal IPv6 address it must be enclosed in square brackets, as in "[2001:db8::1]:80" or "[fe80::1%zone]:80". The zone specifies the scope of the literal IPv6 address as defined in RFC 4007. The functions JoinHostPort and SplitHostPort manipulate a pair of host and port in this form. When using TCP, and the host resolves to multiple IP addresses, Dial will try each IP address in order until one succeeds.

Examples: 

Dial("tcp", "golang.org:http")
Dial("tcp", "192.0.2.1:http")
Dial("tcp", "198.51.100.1:80")
Dial("udp", "[2001:db8::1]:domain")
Dial("udp", "[fe80::1%lo0]:53")
Dial("tcp", ":80")

For IP networks, the network must be "ip", "ip4" or "ip6" followed by a colon and a literal protocol number or a protocol name, and the address has the form "host". The host must be a literal IP address or a literal IPv6 address with zone. It depends on each operating system how the operating system behaves with a non-well known protocol number such as "0" or "255".

Examples: 

Dial("ip4:1", "192.0.2.1")
Dial("ip6:ipv6-icmp", "2001:db8::1")
Dial("ip6:58", "fe80::1%lo0")

For TCP, UDP and IP networks, if the host is empty or a literal unspecified IP address, as in ":80", "0.0.0.0:80" or "[::]:80" for TCP and UDP, "", "0.0.0.0" or "::" for IP, the local system is assumed.

For Unix networks, the address must be a file system path.

func DialTimeout

func DialTimeout(network, address string, timeout time.Duration) (Conn, error)

DialTimeout acts like Dial but takes a timeout.

The timeout includes name resolution, if required. When using TCP, and the host in the address parameter resolves to multiple IP addresses, the timeout is spread over each consecutive dial, such that each is given an appropriate fraction of the time to connect.

See func Dial for a description of the network and address parameters.

func FileConn

func FileConn(f *os.File) (c Conn, err error)

FileConn returns a copy of the network connection corresponding to the open file f. It is the caller's responsibility to close f when finished. Closing c does not affect f, and closing f does not affect c.

type DNSConfigError

type DNSConfigError struct {
	Err error
}

DNSConfigError represents an error reading the machine's DNS configuration. (No longer used; kept for compatibility.)

func (*DNSConfigError) Error

func (e *DNSConfigError) Error() string

func (*DNSConfigError) Temporary

func (e *DNSConfigError) Temporary() bool

func (*DNSConfigError) Timeout

func (e *DNSConfigError) Timeout() bool

func (*DNSConfigError) Unwrap

func (e *DNSConfigError) Unwrap() error

type DNSError

type DNSError struct {
	Err         string // description of the error
	Name        string // name looked for
	Server      string // server used
	IsTimeout   bool   // if true, timed out; not all timeouts set this
	IsTemporary bool   // if true, error is temporary; not all errors set this

	// IsNotFound is set to true when the requested name does not
	// contain any records of the requested type (data not found),
	// or the name itself was not found (NXDOMAIN).
	IsNotFound bool
}

DNSError represents a DNS lookup error.

func (*DNSError) Error

func (e *DNSError) Error() string

func (*DNSError) Temporary

func (e *DNSError) Temporary() bool

Temporary reports whether the DNS error is known to be temporary. This is not always known; a DNS lookup may fail due to a temporary error and return a DNSError for which Temporary returns false.

func (*DNSError) Timeout

func (e *DNSError) Timeout() bool

Timeout reports whether the DNS lookup is known to have timed out. This is not always known; a DNS lookup may fail due to a timeout and return a DNSError for which Timeout returns false.

type Dialer

type Dialer struct {
	// Timeout is the maximum amount of time a dial will wait for
	// a connect to complete. If Deadline is also set, it may fail
	// earlier.
	//
	// The default is no timeout.
	//
	// When using TCP and dialing a host name with multiple IP
	// addresses, the timeout may be divided between them.
	//
	// With or without a timeout, the operating system may impose
	// its own earlier timeout. For instance, TCP timeouts are
	// often around 3 minutes.
	Timeout time.Duration

	// Deadline is the absolute point in time after which dials
	// will fail. If Timeout is set, it may fail earlier.
	// Zero means no deadline, or dependent on the operating system
	// as with the Timeout option.
	Deadline time.Time

	// LocalAddr is the local address to use when dialing an
	// address. The address must be of a compatible type for the
	// network being dialed.
	// If nil, a local address is automatically chosen.
	LocalAddr Addr

	// DualStack previously enabled RFC 6555 Fast Fallback
	// support, also known as "Happy Eyeballs", in which IPv4 is
	// tried soon if IPv6 appears to be misconfigured and
	// hanging.
	//
	// Deprecated: Fast Fallback is enabled by default. To
	// disable, set FallbackDelay to a negative value.
	DualStack bool

	// FallbackDelay specifies the length of time to wait before
	// spawning a RFC 6555 Fast Fallback connection. That is, this
	// is the amount of time to wait for IPv6 to succeed before
	// assuming that IPv6 is misconfigured and falling back to
	// IPv4.
	//
	// If zero, a default delay of 300ms is used.
	// A negative value disables Fast Fallback support.
	FallbackDelay time.Duration

	// KeepAlive specifies the interval between keep-alive
	// probes for an active network connection.
	// If zero, keep-alive probes are sent with a default value
	// (currently 15 seconds), if supported by the protocol and operating
	// system. Network protocols or operating systems that do
	// not support keep-alives ignore this field.
	// If negative, keep-alive probes are disabled.
	KeepAlive time.Duration

	// Resolver optionally specifies an alternate resolver to use.
	Resolver *Resolver

	// Cancel is an optional channel whose closure indicates that
	// the dial should be canceled. Not all types of dials support
	// cancellation.
	//
	// Deprecated: Use DialContext instead.
	Cancel <-chan struct{}

	// If Control is not nil, it is called after creating the network
	// connection but before actually dialing.
	//
	// Network and address parameters passed to Control function are not
	// necessarily the ones passed to Dial. For example, passing "tcp" to Dial
	// will cause the Control function to be called with "tcp4" or "tcp6".
	//
	// Control is ignored if ControlContext is not nil.
	Control func(network, address string, c syscall.RawConn) error

	// If ControlContext is not nil, it is called after creating the network
	// connection but before actually dialing.
	//
	// Network and address parameters passed to ControlContext function are not
	// necessarily the ones passed to Dial. For example, passing "tcp" to Dial
	// will cause the ControlContext function to be called with "tcp4" or "tcp6".
	//
	// If ControlContext is not nil, Control is ignored.
	ControlContext func(ctx context.Context, network, address string, c syscall.RawConn) error
	// contains filtered or unexported fields
}

A Dialer contains options for connecting to an address.

The zero value for each field is equivalent to dialing without that option. Dialing with the zero value of Dialer is therefore equivalent to just calling the Dial function.

It is safe to call Dialer's methods concurrently.

Example 
package main

import (
	"context"
	"log"
	"net"
	"time"
)

func main() {
	var d net.Dialer
	ctx, cancel := context.WithTimeout(context.Background(), time.Minute)
	defer cancel()

	conn, err := d.DialContext(ctx, "tcp", "localhost:12345")
	if err != nil {
		log.Fatalf("Failed to dial: %v", err)
	}
	defer conn.Close()

	if _, err := conn.Write([]byte("Hello, World!")); err != nil {
		log.Fatal(err)
	}
}
Example (Unix) 
package main

import (
	"context"
	"log"
	"net"
	"time"
)

func main() {
	// DialUnix does not take a context.Context parameter. This example shows
	// how to dial a Unix socket with a Context. Note that the Context only
	// applies to the dial operation; it does not apply to the connection once
	// it has been established.
	var d net.Dialer
	ctx, cancel := context.WithTimeout(context.Background(), time.Minute)
	defer cancel()

	d.LocalAddr = nil // if you have a local addr, add it here
	raddr := net.UnixAddr{Name: "/path/to/unix.sock", Net: "unix"}
	conn, err := d.DialContext(ctx, "unix", raddr.String())
	if err != nil {
		log.Fatalf("Failed to dial: %v", err)
	}
	defer conn.Close()
	if _, err := conn.Write([]byte("Hello, socket!")); err != nil {
		log.Fatal(err)
	}
}

func (*Dialer) Dial

func (d *Dialer) Dial(network, address string) (Conn, error)

Dial connects to the address on the named network.

See func Dial for a description of the network and address parameters.

Dial uses context.Background internally; to specify the context, use Dialer.DialContext.

func (*Dialer) DialContext

func (d *Dialer) DialContext(ctx context.Context, network, address string) (Conn, error)

DialContext connects to the address on the named network using the provided context.

The provided Context must be non-nil. If the context expires before the connection is complete, an error is returned. Once successfully connected, any expiration of the context will not affect the connection.

When using TCP, and the host in the address parameter resolves to multiple network addresses, any dial timeout (from d.Timeout or ctx) is spread over each consecutive dial, such that each is given an appropriate fraction of the time to connect. For example, if a host has 4 IP addresses and the timeout is 1 minute, the connect to each single address will be given 15 seconds to complete before trying the next one.

See func Dial for a description of the network and address parameters.

func (*Dialer) MultipathTCP

func (d *Dialer) MultipathTCP() bool

MultipathTCP reports whether MPTCP will be used.

This method doesn't check if MPTCP is supported by the operating system or not.

func (*Dialer) SetMultipathTCP

func (d *Dialer) SetMultipathTCP(use bool)

SetMultipathTCP directs the Dial methods to use, or not use, MPTCP, if supported by the operating system. This method overrides the system default and the GODEBUG=multipathtcp=... setting if any.

If MPTCP is not available on the host or not supported by the server, the Dial methods will fall back to TCP.

type Error

type Error interface {
	error
	Timeout() bool // Is the error a timeout?

	// Deprecated: Temporary errors are not well-defined.
	// Most "temporary" errors are timeouts, and the few exceptions are surprising.
	// Do not use this method.
	Temporary() bool
}

An Error represents a network error.

type Flags

type Flags uint
const (
	FlagUp           Flags = 1 << iota // interface is administratively up
	FlagBroadcast                      // interface supports broadcast access capability
	FlagLoopback                       // interface is a loopback interface
	FlagPointToPoint                   // interface belongs to a point-to-point link
	FlagMulticast                      // interface supports multicast access capability
	FlagRunning                        // interface is in running state
)

func (Flags) String

func (f Flags) String() string

type HardwareAddr

type HardwareAddr []byte

A HardwareAddr represents a physical hardware address.

func ParseMAC

func ParseMAC(s string) (hw HardwareAddr, err error)

ParseMAC parses s as an IEEE 802 MAC-48, EUI-48, EUI-64, or a 20-octet IP over InfiniBand link-layer address using one of the following formats: 

00:00:5e:00:53:01
02:00:5e:10:00:00:00:01
00:00:00:00:fe:80:00:00:00:00:00:00:02:00:5e:10:00:00:00:01
00-00-5e-00-53-01
02-00-5e-10-00-00-00-01
00-00-00-00-fe-80-00-00-00-00-00-00-02-00-5e-10-00-00-00-01
0000.5e00.5301
0200.5e10.0000.0001
0000.0000.fe80.0000.0000.0000.0200.5e10.0000.0001

func (HardwareAddr) String

func (a HardwareAddr) String() string

type IP

type IP []byte

An IP is a single IP address, a slice of bytes. Functions in this package accept either 4-byte (IPv4) or 16-byte (IPv6) slices as input.

Note that in this documentation, referring to an IP address as an IPv4 address or an IPv6 address is a semantic property of the address, not just the length of the byte slice: a 16-byte slice can still be an IPv4 address.

Example (To4) 
package main

import (
	"fmt"
	"net"
)

func main() {
	ipv6 := net.IP{0xfc, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
	ipv4 := net.IPv4(10, 255, 0, 0)

	fmt.Println(ipv6.To4())
	fmt.Println(ipv4.To4())

}

Output:

<nil>
10.255.0.0

func IPv4

func IPv4(a, b, c, d byte) IP

IPv4 returns the IP address (in 16-byte form) of the IPv4 address a.b.c.d.

Example 
package main

import (
	"fmt"
	"net"
)

func main() {
	fmt.Println(net.IPv4(8, 8, 8, 8))

}

Output:

8.8.8.8

func LookupIP

func LookupIP(host string) ([]IP, error)

LookupIP looks up host using the local resolver. It returns a slice of that host's IPv4 and IPv6 addresses.

func ParseIP

func ParseIP(s string) IP

ParseIP parses s as an IP address, returning the result. The string s can be in IPv4 dotted decimal ("192.0.2.1"), IPv6 ("2001:db8::68"), or IPv4-mapped IPv6 ("::ffff:192.0.2.1") form. If s is not a valid textual representation of an IP address, ParseIP returns nil.

Example 
package main

import (
	"fmt"
	"net"
)

func main() {
	fmt.Println(net.ParseIP("192.0.2.1"))
	fmt.Println(net.ParseIP("2001:db8::68"))
	fmt.Println(net.ParseIP("192.0.2"))

}

Output:

192.0.2.1
2001:db8::68
<nil>

func (IP) DefaultMask

func (ip IP) DefaultMask() IPMask

DefaultMask returns the default IP mask for the IP address ip. Only IPv4 addresses have default masks; DefaultMask returns nil if ip is not a valid IPv4 address.

Example 
package main

import (
	"fmt"
	"net"
)

func main() {
	ip := net.ParseIP("192.0.2.1")
	fmt.Println(ip.DefaultMask())

}

Output:

ffffff00

func (IP) Equal

func (ip IP) Equal(x IP) bool

Equal reports whether ip and x are the same IP address. An IPv4 address and that same address in IPv6 form are considered to be equal.

Example 
package main

import (
	"fmt"
	"net"
)

func main() {
	ipv4DNS := net.ParseIP("8.8.8.8")
	ipv4Lo := net.ParseIP("127.0.0.1")
	ipv6DNS := net.ParseIP("0:0:0:0:0:FFFF:0808:0808")

	fmt.Println(ipv4DNS.Equal(ipv4DNS))
	fmt.Println(ipv4DNS.Equal(ipv4Lo))
	fmt.Println(ipv4DNS.Equal(ipv6DNS))

}

Output:

true
false
true

func (IP) IsGlobalUnicast

func (ip IP) IsGlobalUnicast() bool

IsGlobalUnicast reports whether ip is a global unicast address.

The identification of global unicast addresses uses address type identification as defined in RFC 1122, RFC 4632 and RFC 4291 with the exception of IPv4 directed broadcast addresses. It returns true even if ip is in IPv4 private address space or local IPv6 unicast address space.

Example 
package main

import (
	"fmt"
	"net"
)

func main() {
	ipv6Global := net.ParseIP("2000::")
	ipv6UniqLocal := net.ParseIP("2000::")
	ipv6Multi := net.ParseIP("FF00::")

	ipv4Private := net.ParseIP("10.255.0.0")
	ipv4Public := net.ParseIP("8.8.8.8")
	ipv4Broadcast := net.ParseIP("255.255.255.255")

	fmt.Println(ipv6Global.IsGlobalUnicast())
	fmt.Println(ipv6UniqLocal.IsGlobalUnicast())
	fmt.Println(ipv6Multi.IsGlobalUnicast())

	fmt.Println(ipv4Private.IsGlobalUnicast())
	fmt.Println(ipv4Public.IsGlobalUnicast())
	fmt.Println(ipv4Broadcast.IsGlobalUnicast())

}

Output:

true
true
false
true
true
false

func (IP) IsInterfaceLocalMulticast

func (ip IP) IsInterfaceLocalMulticast() bool

IsInterfaceLocalMulticast reports whether ip is an interface-local multicast address.

Example 
package main

import (
	"fmt"
	"net"
)

func main() {
	ipv6InterfaceLocalMulti := net.ParseIP("ff01::1")
	ipv6Global := net.ParseIP("2000::")
	ipv4 := net.ParseIP("255.0.0.0")

	fmt.Println(ipv6InterfaceLocalMulti.IsInterfaceLocalMulticast())
	fmt.Println(ipv6Global.IsInterfaceLocalMulticast())
	fmt.Println(ipv4.IsInterfaceLocalMulticast())

}

Output:

true
false
false

func (IP) IsLinkLocalMulticast

func (ip IP) IsLinkLocalMulticast() bool

IsLinkLocalMulticast reports whether ip is a link-local multicast address.

Example 
package main

import (
	"fmt"
	"net"
)

func main() {
	ipv6LinkLocalMulti := net.ParseIP("ff02::2")
	ipv6LinkLocalUni := net.ParseIP("fe80::")
	ipv4LinkLocalMulti := net.ParseIP("224.0.0.0")
	ipv4LinkLocalUni := net.ParseIP("169.254.0.0")

	fmt.Println(ipv6LinkLocalMulti.IsLinkLocalMulticast())
	fmt.Println(ipv6LinkLocalUni.IsLinkLocalMulticast())
	fmt.Println(ipv4LinkLocalMulti.IsLinkLocalMulticast())
	fmt.Println(ipv4LinkLocalUni.IsLinkLocalMulticast())

}

Output:

true
false
true
false

func (IP) IsLinkLocalUnicast

func (ip IP) IsLinkLocalUnicast() bool

IsLinkLocalUnicast reports whether ip is a link-local unicast address.

Example 
package main

import (
	"fmt"
	"net"
)

func main() {
	ipv6LinkLocalUni := net.ParseIP("fe80::")
	ipv6Global := net.ParseIP("2000::")
	ipv4LinkLocalUni := net.ParseIP("169.254.0.0")
	ipv4LinkLocalMulti := net.ParseIP("224.0.0.0")

	fmt.Println(ipv6LinkLocalUni.IsLinkLocalUnicast())
	fmt.Println(ipv6Global.IsLinkLocalUnicast())
	fmt.Println(ipv4LinkLocalUni.IsLinkLocalUnicast())
	fmt.Println(ipv4LinkLocalMulti.IsLinkLocalUnicast())

}

Output:

true
false
true
false

func (IP) IsLoopback

func (ip IP) IsLoopback() bool

IsLoopback reports whether ip is a loopback address.

Example 
package main

import (
	"fmt"
	"net"
)

func main() {
	ipv6Lo := net.ParseIP("::1")
	ipv6 := net.ParseIP("ff02::1")
	ipv4Lo := net.ParseIP("127.0.0.0")
	ipv4 := net.ParseIP("128.0.0.0")

	fmt.Println(ipv6Lo.IsLoopback())
	fmt.Println(ipv6.IsLoopback())
	fmt.Println(ipv4Lo.IsLoopback())
	fmt.Println(ipv4.IsLoopback())

}

Output:

true
false
true
false

func (IP) IsMulticast

func (ip IP) IsMulticast() bool

IsMulticast reports whether ip is a multicast address.

Example 
package main

import (
	"fmt"
	"net"
)

func main() {
	ipv6Multi := net.ParseIP("FF00::")
	ipv6LinkLocalMulti := net.ParseIP("ff02::1")
	ipv6Lo := net.ParseIP("::1")
	ipv4Multi := net.ParseIP("239.0.0.0")
	ipv4LinkLocalMulti := net.ParseIP("224.0.0.0")
	ipv4Lo := net.ParseIP("127.0.0.0")

	fmt.Println(ipv6Multi.IsMulticast())
	fmt.Println(ipv6LinkLocalMulti.IsMulticast())
	fmt.Println(ipv6Lo.IsMulticast())
	fmt.Println(ipv4Multi.IsMulticast())
	fmt.Println(ipv4LinkLocalMulti.IsMulticast())
	fmt.Println(ipv4Lo.IsMulticast())

}

Output:

true
true
false
true
true
false

func (IP) IsPrivate

func (ip IP) IsPrivate() bool

IsPrivate reports whether ip is a private address, according to RFC 1918 (IPv4 addresses) and RFC 4193 (IPv6 addresses).

Example 
package main

import (
	"fmt"
	"net"
)

func main() {
	ipv6Private := net.ParseIP("fc00::")
	ipv6Public := net.ParseIP("fe00::")
	ipv4Private := net.ParseIP("10.255.0.0")
	ipv4Public := net.ParseIP("11.0.0.0")

	fmt.Println(ipv6Private.IsPrivate())
	fmt.Println(ipv6Public.IsPrivate())
	fmt.Println(ipv4Private.IsPrivate())
	fmt.Println(ipv4Public.IsPrivate())

}

Output:

true
false
true
false

func (IP) IsUnspecified

func (ip IP) IsUnspecified() bool

IsUnspecified reports whether ip is an unspecified address, either the IPv4 address "0.0.0.0" or the IPv6 address "::".

Example 
package main

import (
	"fmt"
	"net"
)

func main() {
	ipv6Unspecified := net.ParseIP("::")
	ipv6Specified := net.ParseIP("fe00::")
	ipv4Unspecified := net.ParseIP("0.0.0.0")
	ipv4Specified := net.ParseIP("8.8.8.8")

	fmt.Println(ipv6Unspecified.IsUnspecified())
	fmt.Println(ipv6Specified.IsUnspecified())
	fmt.Println(ipv4Unspecified.IsUnspecified())
	fmt.Println(ipv4Specified.IsUnspecified())

}

Output:

true
false
true
false

func (IP) MarshalText

func (ip IP) MarshalText() ([]byte, error)

MarshalText implements the encoding.TextMarshaler interface. The encoding is the same as returned by IP.String, with one exception: When len(ip) is zero, it returns an empty slice.

func (IP) Mask

func (ip IP) Mask(mask IPMask) IP

Mask returns the result of masking the IP address ip with mask.

Example 
package main

import (
	"fmt"
	"net"
)

func main() {
	ipv4Addr := net.ParseIP("192.0.2.1")
	// This mask corresponds to a /24 subnet for IPv4.
	ipv4Mask := net.CIDRMask(24, 32)
	fmt.Println(ipv4Addr.Mask(ipv4Mask))

	ipv6Addr := net.ParseIP("2001:db8:a0b:12f0::1")
	// This mask corresponds to a /32 subnet for IPv6.
	ipv6Mask := net.CIDRMask(32, 128)
	fmt.Println(ipv6Addr.Mask(ipv6Mask))

}

Output:

192.0.2.0
2001:db8::

func (IP) String

func (ip IP) String() string

String returns the string form of the IP address ip. It returns one of 4 forms:

Example 
package main

import (
	"fmt"
	"net"
)

func main() {
	ipv6 := net.IP{0xfc, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
	ipv4 := net.IPv4(10, 255, 0, 0)

	fmt.Println(ipv6.String())
	fmt.Println(ipv4.String())

}

Output:

fc00::
10.255.0.0

func (IP) To16

func (ip IP) To16() IP

To16 converts the IP address ip to a 16-byte representation. If ip is not an IP address (it is the wrong length), To16 returns nil.

Example 
package main

import (
	"fmt"
	"net"
)

func main() {
	ipv6 := net.IP{0xfc, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
	ipv4 := net.IPv4(10, 255, 0, 0)

	fmt.Println(ipv6.To16())
	fmt.Println(ipv4.To16())

}

Output:

fc00::
10.255.0.0

func (IP) To4

func (ip IP) To4() IP

To4 converts the IPv4 address ip to a 4-byte representation. If ip is not an IPv4 address, To4 returns nil.

func (*IP) UnmarshalText

func (ip *IP) UnmarshalText(text []byte) error

UnmarshalText implements the encoding.TextUnmarshaler interface. The IP address is expected in a form accepted by ParseIP.

type IPAddr

type IPAddr struct {
	IP   IP
	Zone string // IPv6 scoped addressing zone
}

IPAddr represents the address of an IP end point.

func ResolveIPAddr

func ResolveIPAddr(network, address string) (*IPAddr, error)

ResolveIPAddr returns an address of IP end point.

The network must be an IP network name.

If the host in the address parameter is not a literal IP address, ResolveIPAddr resolves the address to an address of IP end point. Otherwise, it parses the address as a literal IP address. The address parameter can use a host name, but this is not recommended, because it will return at most one of the host name's IP addresses.

See func Dial for a description of the network and address parameters.

func (*IPAddr) Network

func (a *IPAddr) Network() string

Network returns the address's network name, "ip".

func (*IPAddr) String

func (a *IPAddr) String() string

type IPConn

type IPConn struct {
	// contains filtered or unexported fields
}

IPConn is the implementation of the Conn and PacketConn interfaces for IP network connections.

func DialIP

func DialIP(network string, laddr, raddr *IPAddr) (*IPConn, error)

DialIP acts like Dial for IP networks.

The network must be an IP network name; see func Dial for details.

If laddr is nil, a local address is automatically chosen. If the IP field of raddr is nil or an unspecified IP address, the local system is assumed.

func ListenIP

func ListenIP(network string, laddr *IPAddr) (*IPConn, error)

ListenIP acts like ListenPacket for IP networks.

The network must be an IP network name; see func Dial for details.

If the IP field of laddr is nil or an unspecified IP address, ListenIP listens on all available IP addresses of the local system except multicast IP addresses.

func (*IPConn) Close

func (c *IPConn) Close() error

Close closes the connection.

func (*IPConn) File

func (c *IPConn) File() (f *os.File, err error)

File returns a copy of the underlying os.File. It is the caller's responsibility to close f when finished. Closing c does not affect f, and closing f does not affect c.

The returned os.File's file descriptor is different from the connection's. Attempting to change properties of the original using this duplicate may or may not have the desired effect.

func (*IPConn) LocalAddr

func (c *IPConn) LocalAddr() Addr

LocalAddr returns the local network address. The Addr returned is shared by all invocations of LocalAddr, so do not modify it.

func (*IPConn) Read

func (c *IPConn) Read(b []byte) (int, error)

Read implements the Conn Read method.

func (*IPConn) ReadFrom

func (c *IPConn) ReadFrom(b []byte) (int, Addr, error)

ReadFrom implements the PacketConn ReadFrom method.

func (*IPConn) ReadFromIP

func (c *IPConn) ReadFromIP(b []byte) (int, *IPAddr, error)

ReadFromIP acts like ReadFrom but returns an IPAddr.

func (*IPConn) ReadMsgIP

func (c *IPConn) ReadMsgIP(b, oob []byte) (n, oobn, flags int, addr *IPAddr, err error)

ReadMsgIP reads a message from c, copying the payload into b and the associated out-of-band data into oob. It returns the number of bytes copied into b, the number of bytes copied into oob, the flags that were set on the message and the source address of the message.

The packages golang.org/x/net/ipv4 and golang.org/x/net/ipv6 can be used to manipulate IP-level socket options in oob.

func (*IPConn) RemoteAddr

func (c *IPConn) RemoteAddr() Addr

RemoteAddr returns the remote network address. The Addr returned is shared by all invocations of RemoteAddr, so do not modify it.

func (*IPConn) SetDeadline

func (c *IPConn) SetDeadline(t time.Time) error

SetDeadline implements the Conn SetDeadline method.

func (*IPConn) SetReadBuffer

func (c *IPConn) SetReadBuffer(bytes int) error

SetReadBuffer sets the size of the operating system's receive buffer associated with the connection.

func (*IPConn) SetReadDeadline

func (c *IPConn) SetReadDeadline(t time.Time) error

SetReadDeadline implements the Conn SetReadDeadline method.

func (*IPConn) SetWriteBuffer

func (c *IPConn) SetWriteBuffer(bytes int) error

SetWriteBuffer sets the size of the operating system's transmit buffer associated with the connection.

func (*IPConn) SetWriteDeadline

func (c *IPConn) SetWriteDeadline(t time.Time) error

SetWriteDeadline implements the Conn SetWriteDeadline method.

func (*IPConn) SyscallConn

func (c *IPConn) SyscallConn() (syscall.RawConn, error)

SyscallConn returns a raw network connection. This implements the syscall.Conn interface.

func (*IPConn) Write

func (c *IPConn) Write(b []byte) (int, error)

Write implements the Conn Write method.

func (*IPConn) WriteMsgIP

func (c *IPConn) WriteMsgIP(b, oob []byte, addr *IPAddr) (n, oobn int, err error)

WriteMsgIP writes a message to addr via c, copying the payload from b and the associated out-of-band data from oob. It returns the number of payload and out-of-band bytes written.

The packages golang.org/x/net/ipv4 and golang.org/x/net/ipv6 can be used to manipulate IP-level socket options in oob.

func (*IPConn) WriteTo

func (c *IPConn) WriteTo(b []byte, addr Addr) (int, error)

WriteTo implements the PacketConn WriteTo method.

func (*IPConn) WriteToIP

func (c *IPConn) WriteToIP(b []byte, addr *IPAddr) (int, error)

WriteToIP acts like IPConn.WriteTo but takes an IPAddr.

type IPMask

type IPMask []byte

An IPMask is a bitmask that can be used to manipulate IP addresses for IP addressing and routing.

See type IPNet and func ParseCIDR for details.

func CIDRMask

func CIDRMask(ones, bits int) IPMask

CIDRMask returns an IPMask consisting of 'ones' 1 bits followed by 0s up to a total length of 'bits' bits. For a mask of this form, CIDRMask is the inverse of IPMask.Size.

Example 
package main

import (
	"fmt"
	"net"
)

func main() {
	// This mask corresponds to a /31 subnet for IPv4.
	fmt.Println(net.CIDRMask(31, 32))

	// This mask corresponds to a /64 subnet for IPv6.
	fmt.Println(net.CIDRMask(64, 128))

}

Output:

fffffffe
ffffffffffffffff0000000000000000

func IPv4Mask

func IPv4Mask(a, b, c, d byte) IPMask

IPv4Mask returns the IP mask (in 4-byte form) of the IPv4 mask a.b.c.d.

Example 
package main

import (
	"fmt"
	"net"
)

func main() {
	fmt.Println(net.IPv4Mask(255, 255, 255, 0))

}

Output:

ffffff00

func (IPMask) Size

func (m IPMask) Size() (ones, bits int)

Size returns the number of leading ones and total bits in the mask. If the mask is not in the canonical form--ones followed by zeros--then Size returns 0, 0.

func (IPMask) String

func (m IPMask) String() string

String returns the hexadecimal form of m, with no punctuation.

type IPNet

type IPNet struct {
	IP   IP     // network number
	Mask IPMask // network mask
}

An IPNet represents an IP network.

func (*IPNet) Contains

func (n *IPNet) Contains(ip IP) bool

Contains reports whether the network includes ip.

func (*IPNet) Network

func (n *IPNet) Network() string

Network returns the address's network name, "ip+net".

func (*IPNet) String

func (n *IPNet) String() string

String returns the CIDR notation of n like "192.0.2.0/24" or "2001:db8::/48" as defined in RFC 4632 and RFC 4291. If the mask is not in the canonical form, it returns the string which consists of an IP address, followed by a slash character and a mask expressed as hexadecimal form with no punctuation like "198.51.100.0/c000ff00".

type Interface

type Interface struct {
	Index        int          // positive integer that starts at one, zero is never used
	MTU          int          // maximum transmission unit
	Name         string       // e.g., "en0", "lo0", "eth0.100"
	HardwareAddr HardwareAddr // IEEE MAC-48, EUI-48 and EUI-64 form
	Flags        Flags        // e.g., FlagUp, FlagLoopback, FlagMulticast
}

Interface represents a mapping between network interface name and index. It also represents network interface facility information.

func InterfaceByIndex

func InterfaceByIndex(index int) (*Interface, error)

InterfaceByIndex returns the interface specified by index.

On Solaris, it returns one of the logical network interfaces sharing the logical data link; for more precision use InterfaceByName.

func InterfaceByName

func InterfaceByName(name string) (*Interface, error)

InterfaceByName returns the interface specified by name.

func Interfaces

func Interfaces() ([]Interface, error)

Interfaces returns a list of the system's network interfaces.

func (*Interface) Addrs

func (ifi *Interface) Addrs() ([]Addr, error)

Addrs returns a list of unicast interface addresses for a specific interface.

func (*Interface) MulticastAddrs

func (ifi *Interface) MulticastAddrs() ([]Addr, error)

MulticastAddrs returns a list of multicast, joined group addresses for a specific interface.

type InvalidAddrError

type InvalidAddrError string

func (InvalidAddrError) Error

func (e InvalidAddrError) Error() string

func (InvalidAddrError) Temporary

func (e InvalidAddrError) Temporary() bool

func (InvalidAddrError) Timeout

func (e InvalidAddrError) Timeout() bool

type ListenConfig

type ListenConfig struct {
	// If Control is not nil, it is called after creating the network
	// connection but before binding it to the operating system.
	//
	// Network and address parameters passed to Control method are not
	// necessarily the ones passed to Listen. For example, passing "tcp" to
	// Listen will cause the Control function to be called with "tcp4" or "tcp6".
	Control func(network, address string, c syscall.RawConn) error

	// KeepAlive specifies the keep-alive period for network
	// connections accepted by this listener.
	// If zero, keep-alives are enabled if supported by the protocol
	// and operating system. Network protocols or operating systems
	// that do not support keep-alives ignore this field.
	// If negative, keep-alives are disabled.
	KeepAlive time.Duration
	// contains filtered or unexported fields
}

ListenConfig contains options for listening to an address.

func (*ListenConfig) Listen

func (lc *ListenConfig) Listen(ctx context.Context, network, address string) (Listener, error)

Listen announces on the local network address.

See func Listen for a description of the network and address parameters.

func (*ListenConfig) ListenPacket

func (lc *ListenConfig) ListenPacket(ctx context.Context, network, address string) (PacketConn, error)

ListenPacket announces on the local network address.

See func ListenPacket for a description of the network and address parameters.

func (*ListenConfig) MultipathTCP

func (lc *ListenConfig) MultipathTCP() bool

MultipathTCP reports whether MPTCP will be used.

This method doesn't check if MPTCP is supported by the operating system or not.

func (*ListenConfig) SetMultipathTCP

func (lc *ListenConfig) SetMultipathTCP(use bool)

SetMultipathTCP directs the Listen method to use, or not use, MPTCP, if supported by the operating system. This method overrides the system default and the GODEBUG=multipathtcp=... setting if any.

If MPTCP is not available on the host or not supported by the client, the Listen method will fall back to TCP.

type Listener

type Listener interface {
	// Accept waits for and returns the next connection to the listener.
	Accept() (Conn, error)

	// Close closes the listener.
	// Any blocked Accept operations will be unblocked and return errors.
	Close() error

	// Addr returns the listener's network address.
	Addr() Addr
}

A Listener is a generic network listener for stream-oriented protocols.

Multiple goroutines may invoke methods on a Listener simultaneously.

Example 
package main

import (
	"io"
	"log"
	"net"
)

func main() {
	// Listen on TCP port 2000 on all available unicast and
	// anycast IP addresses of the local system.
	l, err := net.Listen("tcp", ":2000")
	if err != nil {
		log.Fatal(err)
	}
	defer l.Close()
	for {
		// Wait for a connection.
		conn, err := l.Accept()
		if err != nil {
			log.Fatal(err)
		}
		// Handle the connection in a new goroutine.
		// The loop then returns to accepting, so that
		// multiple connections may be served concurrently.
		go func(c net.Conn) {
			// Echo all incoming data.
			io.Copy(c, c)
			// Shut down the connection.
			c.Close()
		}(conn)
	}
}

func FileListener

func FileListener(f *os.File) (ln Listener, err error)

FileListener returns a copy of the network listener corresponding to the open file f. It is the caller's responsibility to close ln when finished. Closing ln does not affect f, and closing f does not affect ln.

func Listen

func Listen(network, address string) (Listener, error)

Listen announces on the local network address.

The network must be "tcp", "tcp4", "tcp6", "unix" or "unixpacket".

For TCP networks, if the host in the address parameter is empty or a literal unspecified IP address, Listen listens on all available unicast and anycast IP addresses of the local system. To only use IPv4, use network "tcp4". The address can use a host name, but this is not recommended, because it will create a listener for at most one of the host's IP addresses. If the port in the address parameter is empty or "0", as in "127.0.0.1:" or "[::1]:0", a port number is automatically chosen. The Addr method of Listener can be used to discover the chosen port.

See func Dial for a description of the network and address parameters.

Listen uses context.Background internally; to specify the context, use ListenConfig.Listen.

type MX

type MX struct {
	Host string
	Pref uint16
}

An MX represents a single DNS MX record.

func LookupMX

func LookupMX(name string) ([]*MX, error)

LookupMX returns the DNS MX records for the given domain name sorted by preference.

The returned mail server names are validated to be properly formatted presentation-format domain names. If the response contains invalid names, those records are filtered out and an error will be returned alongside the remaining results, if any.

LookupMX uses context.Background internally; to specify the context, use Resolver.LookupMX.

type NS

type NS struct {
	Host string
}

An NS represents a single DNS NS record.

func LookupNS

func LookupNS(name string) ([]*NS, error)

LookupNS returns the DNS NS records for the given domain name.

The returned name server names are validated to be properly formatted presentation-format domain names. If the response contains invalid names, those records are filtered out and an error will be returned alongside the remaining results, if any.

LookupNS uses context.Background internally; to specify the context, use Resolver.LookupNS.

type OpError

type OpError struct {
	// Op is the operation which caused the error, such as
	// "read" or "write".
	Op string

	// Net is the network type on which this error occurred,
	// such as "tcp" or "udp6".
	Net string

	// For operations involving a remote network connection, like
	// Dial, Read, or Write, Source is the corresponding local
	// network address.
	Source Addr

	// Addr is the network address for which this error occurred.
	// For local operations, like Listen or SetDeadline, Addr is
	// the address of the local endpoint being manipulated.
	// For operations involving a remote network connection, like
	// Dial, Read, or Write, Addr is the remote address of that
	// connection.
	Addr Addr

	// Err is the error that occurred during the operation.
	// The Error method panics if the error is nil.
	Err error
}

OpError is the error type usually returned by functions in the net package. It describes the operation, network type, and address of an error.

func (*OpError) Error

func (e *OpError) Error() string

func (*OpError) Temporary

func (e *OpError) Temporary() bool

func (*OpError) Timeout

func (e *OpError) Timeout() bool

func (*OpError) Unwrap

func (e *OpError) Unwrap() error

type PacketConn

type PacketConn interface {
	// ReadFrom reads a packet from the connection,
	// copying the payload into p. It returns the number of
	// bytes copied into p and the return address that
	// was on the packet.
	// It returns the number of bytes read (0 <= n <= len(p))
	// and any error encountered. Callers should always process
	// the n > 0 bytes returned before considering the error err.
	// ReadFrom can be made to time out and return an error after a
	// fixed time limit; see SetDeadline and SetReadDeadline.
	ReadFrom(p []byte) (n int, addr Addr, err error)

	// WriteTo writes a packet with payload p to addr.
	// WriteTo can be made to time out and return an Error after a
	// fixed time limit; see SetDeadline and SetWriteDeadline.
	// On packet-oriented connections, write timeouts are rare.
	WriteTo(p []byte, addr Addr) (n int, err error)

	// Close closes the connection.
	// Any blocked ReadFrom or WriteTo operations will be unblocked and return errors.
	Close() error

	// LocalAddr returns the local network address, if known.
	LocalAddr() Addr

	// SetDeadline sets the read and write deadlines associated
	// with the connection. It is equivalent to calling both
	// SetReadDeadline and SetWriteDeadline.
	//
	// A deadline is an absolute time after which I/O operations
	// fail instead of blocking. The deadline applies to all future
	// and pending I/O, not just the immediately following call to
	// Read or Write. After a deadline has been exceeded, the
	// connection can be refreshed by setting a deadline in the future.
	//
	// If the deadline is exceeded a call to Read or Write or to other
	// I/O methods will return an error that wraps os.ErrDeadlineExceeded.
	// This can be tested using errors.Is(err, os.ErrDeadlineExceeded).
	// The error's Timeout method will return true, but note that there
	// are other possible errors for which the Timeout method will
	// return true even if the deadline has not been exceeded.
	//
	// An idle timeout can be implemented by repeatedly extending
	// the deadline after successful ReadFrom or WriteTo calls.
	//
	// A zero value for t means I/O operations will not time out.
	SetDeadline(t time.Time) error

	// SetReadDeadline sets the deadline for future ReadFrom calls
	// and any currently-blocked ReadFrom call.
	// A zero value for t means ReadFrom will not time out.
	SetReadDeadline(t time.Time) error

	// SetWriteDeadline sets the deadline for future WriteTo calls
	// and any currently-blocked WriteTo call.
	// Even if write times out, it may return n > 0, indicating that
	// some of the data was successfully written.
	// A zero value for t means WriteTo will not time out.
	SetWriteDeadline(t time.Time) error
}

PacketConn is a generic packet-oriented network connection.

Multiple goroutines may invoke methods on a PacketConn simultaneously.

func FilePacketConn

func FilePacketConn(f *os.File) (c PacketConn, err error)

FilePacketConn returns a copy of the packet network connection corresponding to the open file f. It is the caller's responsibility to close f when finished. Closing c does not affect f, and closing f does not affect c.

func ListenPacket

func ListenPacket(network, address string) (PacketConn, error)

ListenPacket announces on the local network address.

The network must be "udp", "udp4", "udp6", "unixgram", or an IP transport. The IP transports are "ip", "ip4", or "ip6" followed by a colon and a literal protocol number or a protocol name, as in "ip:1" or "ip:icmp".

For UDP and IP networks, if the host in the address parameter is empty or a literal unspecified IP address, ListenPacket listens on all available IP addresses of the local system except multicast IP addresses. To only use IPv4, use network "udp4" or "ip4:proto". The address can use a host name, but this is not recommended, because it will create a listener for at most one of the host's IP addresses. If the port in the address parameter is empty or "0", as in "127.0.0.1:" or "[::1]:0", a port number is automatically chosen. The LocalAddr method of PacketConn can be used to discover the chosen port.

See func Dial for a description of the network and address parameters.

ListenPacket uses context.Background internally; to specify the context, use ListenConfig.ListenPacket.

type ParseError

type ParseError struct {
	// Type is the type of string that was expected, such as
	// "IP address", "CIDR address".
	Type string

	// Text is the malformed text string.
	Text string
}

A ParseError is the error type of literal network address parsers.

func (*ParseError) Error

func (e *ParseError) Error() string

func (*ParseError) Temporary

func (e *ParseError) Temporary() bool

func (*ParseError) Timeout

func (e *ParseError) Timeout() bool

type Resolver

type Resolver struct {
	// PreferGo controls whether Go's built-in DNS resolver is preferred
	// on platforms where it's available. It is equivalent to setting
	// GODEBUG=netdns=go, but scoped to just this resolver.
	PreferGo bool

	// StrictErrors controls the behavior of temporary errors
	// (including timeout, socket errors, and SERVFAIL) when using
	// Go's built-in resolver. For a query composed of multiple
	// sub-queries (such as an A+AAAA address lookup, or walking the
	// DNS search list), this option causes such errors to abort the
	// whole query instead of returning a partial result. This is
	// not enabled by default because it may affect compatibility
	// with resolvers that process AAAA queries incorrectly.
	StrictErrors bool

	// Dial optionally specifies an alternate dialer for use by
	// Go's built-in DNS resolver to make TCP and UDP connections
	// to DNS services. The host in the address parameter will
	// always be a literal IP address and not a host name, and the
	// port in the address parameter will be a literal port number
	// and not a service name.
	// If the Conn returned is also a PacketConn, sent and received DNS
	// messages must adhere to RFC 1035 section 4.2.1, "UDP usage".
	// Otherwise, DNS messages transmitted over Conn must adhere
	// to RFC 7766 section 5, "Transport Protocol Selection".
	// If nil, the default dialer is used.
	Dial func(ctx context.Context, network, address string) (Conn, error)
	// contains filtered or unexported fields
}

A Resolver looks up names and numbers.

A nil *Resolver is equivalent to a zero Resolver.

func (*Resolver) LookupAddr

func (r *Resolver) LookupAddr(ctx context.Context, addr string) ([]string, error)

LookupAddr performs a reverse lookup for the given address, returning a list of names mapping to that address.

The returned names are validated to be properly formatted presentation-format domain names. If the response contains invalid names, those records are filtered out and an error will be returned alongside the remaining results, if any.

func (*Resolver) LookupCNAME

func (r *Resolver) LookupCNAME(ctx context.Context, host string) (string, error)

LookupCNAME returns the canonical name for the given host. Callers that do not care about the canonical name can call LookupHost or LookupIP directly; both take care of resolving the canonical name as part of the lookup.

A canonical name is the final name after following zero or more CNAME records. LookupCNAME does not return an error if host does not contain DNS "CNAME" records, as long as host resolves to address records.

The returned canonical name is validated to be a properly formatted presentation-format domain name.

func (*Resolver) LookupHost

func (r *Resolver) LookupHost(ctx context.Context, host string) (addrs []string, err error)

LookupHost looks up the given host using the local resolver. It returns a slice of that host's addresses.

func (*Resolver) LookupIP

func (r *Resolver) LookupIP(ctx context.Context, network, host string) ([]IP, error)

LookupIP looks up host for the given network using the local resolver. It returns a slice of that host's IP addresses of the type specified by network. network must be one of "ip", "ip4" or "ip6".

func (*Resolver) LookupIPAddr

func (r *Resolver) LookupIPAddr(ctx context.Context, host string) ([]IPAddr, error)

LookupIPAddr looks up host using the local resolver. It returns a slice of that host's IPv4 and IPv6 addresses.

func (*Resolver) LookupMX

func (r *Resolver) LookupMX(ctx context.Context, name string) ([]*MX, error)

LookupMX returns the DNS MX records for the given domain name sorted by preference.

The returned mail server names are validated to be properly formatted presentation-format domain names. If the response contains invalid names, those records are filtered out and an error will be returned alongside the remaining results, if any.

func (*Resolver) LookupNS

func (r *Resolver) LookupNS(ctx context.Context, name string) ([]*NS, error)

LookupNS returns the DNS NS records for the given domain name.

The returned name server names are validated to be properly formatted presentation-format domain names. If the response contains invalid names, those records are filtered out and an error will be returned alongside the remaining results, if any.

func (*Resolver) LookupNetIP

func (r *Resolver) LookupNetIP(ctx context.Context, network, host string) ([]netip.Addr, error)

LookupNetIP looks up host using the local resolver. It returns a slice of that host's IP addresses of the type specified by network. The network must be one of "ip", "ip4" or "ip6".

func (*Resolver) LookupPort

func (r *Resolver) LookupPort(ctx context.Context, network, service string) (port int, err error)

LookupPort looks up the port for the given network and service.

The network must be one of "tcp", "tcp4", "tcp6", "udp", "udp4", "udp6" or "ip".

func (*Resolver) LookupSRV

func (r *Resolver) LookupSRV(ctx context.Context, service, proto, name string) (string, []*SRV, error)

LookupSRV tries to resolve an SRV query of the given service, protocol, and domain name. The proto is "tcp" or "udp". The returned records are sorted by priority and randomized by weight within a priority.

LookupSRV constructs the DNS name to look up following RFC 2782. That is, it looks up _service._proto.name. To accommodate services publishing SRV records under non-standard names, if both service and proto are empty strings, LookupSRV looks up name directly.

The returned service names are validated to be properly formatted presentation-format domain names. If the response contains invalid names, those records are filtered out and an error will be returned alongside the remaining results, if any.

func (*Resolver) LookupTXT

func (r *Resolver) LookupTXT(ctx context.Context, name string) ([]string, error)

LookupTXT returns the DNS TXT records for the given domain name.

type SRV

type SRV struct {
	Target   string
	Port     uint16
	Priority uint16
	Weight   uint16
}

An SRV represents a single DNS SRV record.

func LookupSRV

func LookupSRV(service, proto, name string) (cname string, addrs []*SRV, err error)

LookupSRV tries to resolve an SRV query of the given service, protocol, and domain name. The proto is "tcp" or "udp". The returned records are sorted by priority and randomized by weight within a priority.

LookupSRV constructs the DNS name to look up following RFC 2782. That is, it looks up _service._proto.name. To accommodate services publishing SRV records under non-standard names, if both service and proto are empty strings, LookupSRV looks up name directly.

The returned service names are validated to be properly formatted presentation-format domain names. If the response contains invalid names, those records are filtered out and an error will be returned alongside the remaining results, if any.

type TCPAddr

type TCPAddr struct {
	IP   IP
	Port int
	Zone string // IPv6 scoped addressing zone
}

TCPAddr represents the address of a TCP end point.

func ResolveTCPAddr

func ResolveTCPAddr(network, address string) (*TCPAddr, error)

ResolveTCPAddr returns an address of TCP end point.

The network must be a TCP network name.

If the host in the address parameter is not a literal IP address or the port is not a literal port number, ResolveTCPAddr resolves the address to an address of TCP end point. Otherwise, it parses the address as a pair of literal IP address and port number. The address parameter can use a host name, but this is not recommended, because it will return at most one of the host name's IP addresses.

See func Dial for a description of the network and address parameters.

func TCPAddrFromAddrPort

func TCPAddrFromAddrPort(addr netip.AddrPort) *TCPAddr

TCPAddrFromAddrPort returns addr as a TCPAddr. If addr.IsValid() is false, then the returned TCPAddr will contain a nil IP field, indicating an address family-agnostic unspecified address.

func (*TCPAddr) AddrPort

func (a *TCPAddr) AddrPort() netip.AddrPort

AddrPort returns the TCPAddr a as a netip.AddrPort.

If a.Port does not fit in a uint16, it's silently truncated.

If a is nil, a zero value is returned.

func (*TCPAddr) Network

func (a *TCPAddr) Network() string

Network returns the address's network name, "tcp".

func (*TCPAddr) String

func (a *TCPAddr) String() string

type TCPConn

type TCPConn struct {
	// contains filtered or unexported fields
}

TCPConn is an implementation of the Conn interface for TCP network connections.

func DialTCP

func DialTCP(network string, laddr, raddr *TCPAddr) (*TCPConn, error)

DialTCP acts like Dial for TCP networks.

The network must be a TCP network name; see func Dial for details.

If laddr is nil, a local address is automatically chosen. If the IP field of raddr is nil or an unspecified IP address, the local system is assumed.

func (*TCPConn) Close

func (c *TCPConn) Close() error

Close closes the connection.

func (*TCPConn) CloseRead

func (c *TCPConn) CloseRead() error

CloseRead shuts down the reading side of the TCP connection. Most callers should just use Close.

func (*TCPConn) CloseWrite

func (c *TCPConn) CloseWrite() error

CloseWrite shuts down the writing side of the TCP connection. Most callers should just use Close.

func (*TCPConn) File

func (c *TCPConn) File() (f *os.File, err error)

File returns a copy of the underlying os.File. It is the caller's responsibility to close f when finished. Closing c does not affect f, and closing f does not affect c.

The returned os.File's file descriptor is different from the connection's. Attempting to change properties of the original using this duplicate may or may not have the desired effect.

func (*TCPConn) LocalAddr

func (c *TCPConn) LocalAddr() Addr

LocalAddr returns the local network address. The Addr returned is shared by all invocations of LocalAddr, so do not modify it.

func (*TCPConn) MultipathTCP

func (c *TCPConn) MultipathTCP() (bool, error)

MultipathTCP reports whether the ongoing connection is using MPTCP.

If Multipath TCP is not supported by the host, by the other peer or intentionally / accidentally filtered out by a device in between, a fallback to TCP will be done. This method does its best to check if MPTCP is still being used or not.

On Linux, more conditions are verified on kernels >= v5.16, improving the results.

func (*TCPConn) Read

func (c *TCPConn) Read(b []byte) (int, error)

Read implements the Conn Read method.

func (*TCPConn) ReadFrom

func (c *TCPConn) ReadFrom(r io.Reader) (int64, error)

ReadFrom implements the io.ReaderFrom ReadFrom method.

func (*TCPConn) RemoteAddr

func (c *TCPConn) RemoteAddr() Addr

RemoteAddr returns the remote network address. The Addr returned is shared by all invocations of RemoteAddr, so do not modify it.

func (*TCPConn) SetDeadline

func (c *TCPConn) SetDeadline(t time.Time) error

SetDeadline implements the Conn SetDeadline method.

func (*TCPConn) SetKeepAlive

func (c *TCPConn) SetKeepAlive(keepalive bool) error

SetKeepAlive sets whether the operating system should send keep-alive messages on the connection.

func (*TCPConn) SetKeepAlivePeriod

func (c *TCPConn) SetKeepAlivePeriod(d time.Duration) error

SetKeepAlivePeriod sets period between keep-alives.

func (*TCPConn) SetLinger

func (c *TCPConn) SetLinger(sec int) error

SetLinger sets the behavior of Close on a connection which still has data waiting to be sent or to be acknowledged.

If sec < 0 (the default), the operating system finishes sending the data in the background.

If sec == 0, the operating system discards any unsent or unacknowledged data.

If sec > 0, the data is sent in the background as with sec < 0. On some operating systems including Linux, this may cause Close to block until all data has been sent or discarded. On some operating systems after sec seconds have elapsed any remaining unsent data may be discarded.

func (*TCPConn) SetNoDelay

func (c *TCPConn) SetNoDelay(noDelay bool) error

SetNoDelay controls whether the operating system should delay packet transmission in hopes of sending fewer packets (Nagle's algorithm). The default is true (no delay), meaning that data is sent as soon as possible after a Write.

func (*TCPConn) SetReadBuffer

func (c *TCPConn) SetReadBuffer(bytes int) error

SetReadBuffer sets the size of the operating system's receive buffer associated with the connection.

func (*TCPConn) SetReadDeadline

func (c *TCPConn) SetReadDeadline(t time.Time) error

SetReadDeadline implements the Conn SetReadDeadline method.

func (*TCPConn) SetWriteBuffer

func (c *TCPConn) SetWriteBuffer(bytes int) error

SetWriteBuffer sets the size of the operating system's transmit buffer associated with the connection.

func (*TCPConn) SetWriteDeadline

func (c *TCPConn) SetWriteDeadline(t time.Time) error

SetWriteDeadline implements the Conn SetWriteDeadline method.

func (*TCPConn) SyscallConn

func (c *TCPConn) SyscallConn() (syscall.RawConn, error)

SyscallConn returns a raw network connection. This implements the syscall.Conn interface.

func (*TCPConn) Write

func (c *TCPConn) Write(b []byte) (int, error)

Write implements the Conn Write method.

func (*TCPConn) WriteTo

func (c *TCPConn) WriteTo(w io.Writer) (int64, error)

WriteTo implements the io.WriterTo WriteTo method.

type TCPListener

type TCPListener struct {
	// contains filtered or unexported fields
}

TCPListener is a TCP network listener. Clients should typically use variables of type Listener instead of assuming TCP.

func ListenTCP

func ListenTCP(network string, laddr *TCPAddr) (*TCPListener, error)

ListenTCP acts like Listen for TCP networks.

The network must be a TCP network name; see func Dial for details.

If the IP field of laddr is nil or an unspecified IP address, ListenTCP listens on all available unicast and anycast IP addresses of the local system. If the Port field of laddr is 0, a port number is automatically chosen.

func (*TCPListener) Accept

func (l *TCPListener) Accept() (Conn, error)

Accept implements the Accept method in the Listener interface; it waits for the next call and returns a generic Conn.

func (*TCPListener) AcceptTCP

func (l *TCPListener) AcceptTCP() (*TCPConn, error)

AcceptTCP accepts the next incoming call and returns the new connection.

func (*TCPListener) Addr

func (l *TCPListener) Addr() Addr

Addr returns the listener's network address, a *TCPAddr. The Addr returned is shared by all invocations of Addr, so do not modify it.

func (*TCPListener) Close

func (l *TCPListener) Close() error

Close stops listening on the TCP address. Already Accepted connections are not closed.

func (*TCPListener) File

func (l *TCPListener) File() (f *os.File, err error)

File returns a copy of the underlying os.File. It is the caller's responsibility to close f when finished. Closing l does not affect f, and closing f does not affect l.

The returned os.File's file descriptor is different from the connection's. Attempting to change properties of the original using this duplicate may or may not have the desired effect.

func (*TCPListener) SetDeadline

func (l *TCPListener) SetDeadline(t time.Time) error

SetDeadline sets the deadline associated with the listener. A zero time value disables the deadline.

func (*TCPListener) SyscallConn

func (l *TCPListener) SyscallConn() (syscall.RawConn, error)

SyscallConn returns a raw network connection. This implements the syscall.Conn interface.

The returned RawConn only supports calling Control. Read and Write return an error.

type UDPAddr

type UDPAddr struct {
	IP   IP
	Port int
	Zone string // IPv6 scoped addressing zone
}

UDPAddr represents the address of a UDP end point.

func ResolveUDPAddr

func ResolveUDPAddr(network, address string) (*UDPAddr, error)

ResolveUDPAddr returns an address of UDP end point.

The network must be a UDP network name.

If the host in the address parameter is not a literal IP address or the port is not a literal port number, ResolveUDPAddr resolves the address to an address of UDP end point. Otherwise, it parses the address as a pair of literal IP address and port number. The address parameter can use a host name, but this is not recommended, because it will return at most one of the host name's IP addresses.

See func Dial for a description of the network and address parameters.

func UDPAddrFromAddrPort

func UDPAddrFromAddrPort(addr netip.AddrPort) *UDPAddr

UDPAddrFromAddrPort returns addr as a UDPAddr. If addr.IsValid() is false, then the returned UDPAddr will contain a nil IP field, indicating an address family-agnostic unspecified address.

func (*UDPAddr) AddrPort

func (a *UDPAddr) AddrPort() netip.AddrPort

AddrPort returns the UDPAddr a as a netip.AddrPort.

If a.Port does not fit in a uint16, it's silently truncated.

If a is nil, a zero value is returned.

func (*UDPAddr) Network

func (a *UDPAddr) Network() string

Network returns the address's network name, "udp".

func (*UDPAddr) String

func (a *UDPAddr) String() string

type UDPConn

type UDPConn struct {
	// contains filtered or unexported fields
}

UDPConn is the implementation of the Conn and PacketConn interfaces for UDP network connections.

func DialUDP

func DialUDP(network string, laddr, raddr *UDPAddr) (*UDPConn, error)

DialUDP acts like Dial for UDP networks.

The network must be a UDP network name; see func Dial for details.

If laddr is nil, a local address is automatically chosen. If the IP field of raddr is nil or an unspecified IP address, the local system is assumed.

func ListenMulticastUDP

func ListenMulticastUDP(network string, ifi *Interface, gaddr *UDPAddr) (*UDPConn, error)

ListenMulticastUDP acts like ListenPacket for UDP networks but takes a group address on a specific network interface.

The network must be a UDP network name; see func Dial for details.

ListenMulticastUDP listens on all available IP addresses of the local system including the group, multicast IP address. If ifi is nil, ListenMulticastUDP uses the system-assigned multicast interface, although this is not recommended because the assignment depends on platforms and sometimes it might require routing configuration. If the Port field of gaddr is 0, a port number is automatically chosen.

ListenMulticastUDP is just for convenience of simple, small applications. There are golang.org/x/net/ipv4 and golang.org/x/net/ipv6 packages for general purpose uses.

Note that ListenMulticastUDP will set the IP_MULTICAST_LOOP socket option to 0 under IPPROTO_IP, to disable loopback of multicast packets.

func ListenUDP

func ListenUDP(network string, laddr *UDPAddr) (*UDPConn, error)

ListenUDP acts like ListenPacket for UDP networks.

The network must be a UDP network name; see func Dial for details.

If the IP field of laddr is nil or an unspecified IP address, ListenUDP listens on all available IP addresses of the local system except multicast IP addresses. If the Port field of laddr is 0, a port number is automatically chosen.

func (*UDPConn) Close

func (c *UDPConn) Close() error

Close closes the connection.

func (*UDPConn) File

func (c *UDPConn) File() (f *os.File, err error)

File returns a copy of the underlying os.File. It is the caller's responsibility to close f when finished. Closing c does not affect f, and closing f does not affect c.

The returned os.File's file descriptor is different from the connection's. Attempting to change properties of the original using this duplicate may or may not have the desired effect.

func (*UDPConn) LocalAddr

func (c *UDPConn) LocalAddr() Addr

LocalAddr returns the local network address. The Addr returned is shared by all invocations of LocalAddr, so do not modify it.

func (*UDPConn) Read

func (c *UDPConn) Read(b []byte) (int, error)

Read implements the Conn Read method.

func (*UDPConn) ReadFrom

func (c *UDPConn) ReadFrom(b []byte) (int, Addr, error)

ReadFrom implements the PacketConn ReadFrom method.

func (*UDPConn) ReadFromUDP

func (c *UDPConn) ReadFromUDP(b []byte) (n int, addr *UDPAddr, err error)

ReadFromUDP acts like ReadFrom but returns a UDPAddr.

func (*UDPConn) ReadFromUDPAddrPort

func (c *UDPConn) ReadFromUDPAddrPort(b []byte) (n int, addr netip.AddrPort, err error)

ReadFromUDPAddrPort acts like ReadFrom but returns a netip.AddrPort.

If c is bound to an unspecified address, the returned netip.AddrPort's address might be an IPv4-mapped IPv6 address. Use netip.Addr.Unmap to get the address without the IPv6 prefix.

func (*UDPConn) ReadMsgUDP

func (c *UDPConn) ReadMsgUDP(b, oob []byte) (n, oobn, flags int, addr *UDPAddr, err error)

ReadMsgUDP reads a message from c, copying the payload into b and the associated out-of-band data into oob. It returns the number of bytes copied into b, the number of bytes copied into oob, the flags that were set on the message and the source address of the message.

The packages golang.org/x/net/ipv4 and golang.org/x/net/ipv6 can be used to manipulate IP-level socket options in oob.

func (*UDPConn) ReadMsgUDPAddrPort

func (c *UDPConn) ReadMsgUDPAddrPort(b, oob []byte) (n, oobn, flags int, addr netip.AddrPort, err error)

ReadMsgUDPAddrPort is like ReadMsgUDP but returns an netip.AddrPort instead of a UDPAddr.

func (*UDPConn) RemoteAddr

func (c *UDPConn) RemoteAddr() Addr

RemoteAddr returns the remote network address. The Addr returned is shared by all invocations of RemoteAddr, so do not modify it.

func (*UDPConn) SetDeadline

func (c *UDPConn) SetDeadline(t time.Time) error

SetDeadline implements the Conn SetDeadline method.

func (*UDPConn) SetReadBuffer

func (c *UDPConn) SetReadBuffer(bytes int) error

SetReadBuffer sets the size of the operating system's receive buffer associated with the connection.

func (*UDPConn) SetReadDeadline

func (c *UDPConn) SetReadDeadline(t time.Time) error

SetReadDeadline implements the Conn SetReadDeadline method.

func (*UDPConn) SetWriteBuffer

func (c *UDPConn) SetWriteBuffer(bytes int) error

SetWriteBuffer sets the size of the operating system's transmit buffer associated with the connection.

func (*UDPConn) SetWriteDeadline

func (c *UDPConn) SetWriteDeadline(t time.Time) error

SetWriteDeadline implements the Conn SetWriteDeadline method.

func (*UDPConn) SyscallConn

func (c *UDPConn) SyscallConn() (syscall.RawConn, error)

SyscallConn returns a raw network connection. This implements the syscall.Conn interface.

func (*UDPConn) Write

func (c *UDPConn) Write(b []byte) (int, error)

Write implements the Conn Write method.

func (*UDPConn) WriteMsgUDP

func (c *UDPConn) WriteMsgUDP(b, oob []byte, addr *UDPAddr) (n, oobn int, err error)

WriteMsgUDP writes a message to addr via c if c isn't connected, or to c's remote address if c is connected (in which case addr must be nil). The payload is copied from b and the associated out-of-band data is copied from oob. It returns the number of payload and out-of-band bytes written.

The packages golang.org/x/net/ipv4 and golang.org/x/net/ipv6 can be used to manipulate IP-level socket options in oob.

func (*UDPConn) WriteMsgUDPAddrPort

func (c *UDPConn) WriteMsgUDPAddrPort(b, oob []byte, addr netip.AddrPort) (n, oobn int, err error)

WriteMsgUDPAddrPort is like WriteMsgUDP but takes a netip.AddrPort instead of a UDPAddr.

func (*UDPConn) WriteTo

func (c *UDPConn) WriteTo(b []byte, addr Addr) (int, error)

WriteTo implements the PacketConn WriteTo method.

Example 
package main

import (
	"log"
	"net"
)

func main() {
	// Unlike Dial, ListenPacket creates a connection without any
	// association with peers.
	conn, err := net.ListenPacket("udp", ":0")
	if err != nil {
		log.Fatal(err)
	}
	defer conn.Close()

	dst, err := net.ResolveUDPAddr("udp", "192.0.2.1:2000")
	if err != nil {
		log.Fatal(err)
	}

	// The connection can write data to the desired address.
	_, err = conn.WriteTo([]byte("data"), dst)
	if err != nil {
		log.Fatal(err)
	}
}

func (*UDPConn) WriteToUDP

func (c *UDPConn) WriteToUDP(b []byte, addr *UDPAddr) (int, error)

WriteToUDP acts like WriteTo but takes a UDPAddr.

func (*UDPConn) WriteToUDPAddrPort

func (c *UDPConn) WriteToUDPAddrPort(b []byte, addr netip.AddrPort) (int, error)

WriteToUDPAddrPort acts like WriteTo but takes a netip.AddrPort.

type UnixAddr

type UnixAddr struct {
	Name string
	Net  string
}

UnixAddr represents the address of a Unix domain socket end point.

func ResolveUnixAddr

func ResolveUnixAddr(network, address string) (*UnixAddr, error)

ResolveUnixAddr returns an address of Unix domain socket end point.

The network must be a Unix network name.

See func Dial for a description of the network and address parameters.

func (*UnixAddr) Network

func (a *UnixAddr) Network() string

Network returns the address's network name, "unix", "unixgram" or "unixpacket".

func (*UnixAddr) String

func (a *UnixAddr) String() string

type UnixConn

type UnixConn struct {
	// contains filtered or unexported fields
}

UnixConn is an implementation of the Conn interface for connections to Unix domain sockets.

func DialUnix

func DialUnix(network string, laddr, raddr *UnixAddr) (*UnixConn, error)

DialUnix acts like Dial for Unix networks.

The network must be a Unix network name; see func Dial for details.

If laddr is non-nil, it is used as the local address for the connection.

func ListenUnixgram

func ListenUnixgram(network string, laddr *UnixAddr) (*UnixConn, error)

ListenUnixgram acts like ListenPacket for Unix networks.

The network must be "unixgram".

func (*UnixConn) Close

func (c *UnixConn) Close() error

Close closes the connection.

func (*UnixConn) CloseRead

func (c *UnixConn) CloseRead() error

CloseRead shuts down the reading side of the Unix domain connection. Most callers should just use Close.

func (*UnixConn) CloseWrite

func (c *UnixConn) CloseWrite() error

CloseWrite shuts down the writing side of the Unix domain connection. Most callers should just use Close.

func (*UnixConn) File

func (c *UnixConn) File() (f *os.File, err error)

File returns a copy of the underlying os.File. It is the caller's responsibility to close f when finished. Closing c does not affect f, and closing f does not affect c.

The returned os.File's file descriptor is different from the connection's. Attempting to change properties of the original using this duplicate may or may not have the desired effect.

func (*UnixConn) LocalAddr

func (c *UnixConn) LocalAddr() Addr

LocalAddr returns the local network address. The Addr returned is shared by all invocations of LocalAddr, so do not modify it.

func (*UnixConn) Read

func (c *UnixConn) Read(b []byte) (int, error)

Read implements the Conn Read method.

func (*UnixConn) ReadFrom

func (c *UnixConn) ReadFrom(b []byte) (int, Addr, error)

ReadFrom implements the PacketConn ReadFrom method.

func (*UnixConn) ReadFromUnix

func (c *UnixConn) ReadFromUnix(b []byte) (int, *UnixAddr, error)

ReadFromUnix acts like UnixConn.ReadFrom but returns a UnixAddr.

func (*UnixConn) ReadMsgUnix

func (c *UnixConn) ReadMsgUnix(b, oob []byte) (n, oobn, flags int, addr *UnixAddr, err error)

ReadMsgUnix reads a message from c, copying the payload into b and the associated out-of-band data into oob. It returns the number of bytes copied into b, the number of bytes copied into oob, the flags that were set on the message and the source address of the message.

Note that if len(b) == 0 and len(oob) > 0, this function will still read (and discard) 1 byte from the connection.

func (*UnixConn) RemoteAddr

func (c *UnixConn) RemoteAddr() Addr

RemoteAddr returns the remote network address. The Addr returned is shared by all invocations of RemoteAddr, so do not modify it.

func (*UnixConn) SetDeadline

func (c *UnixConn) SetDeadline(t time.Time) error

SetDeadline implements the Conn SetDeadline method.

func (*UnixConn) SetReadBuffer

func (c *UnixConn) SetReadBuffer(bytes int) error

SetReadBuffer sets the size of the operating system's receive buffer associated with the connection.

func (*UnixConn) SetReadDeadline

func (c *UnixConn) SetReadDeadline(t time.Time) error

SetReadDeadline implements the Conn SetReadDeadline method.

func (*UnixConn) SetWriteBuffer

func (c *UnixConn) SetWriteBuffer(bytes int) error

SetWriteBuffer sets the size of the operating system's transmit buffer associated with the connection.

func (*UnixConn) SetWriteDeadline

func (c *UnixConn) SetWriteDeadline(t time.Time) error

SetWriteDeadline implements the Conn SetWriteDeadline method.

func (*UnixConn) SyscallConn

func (c *UnixConn) SyscallConn() (syscall.RawConn, error)

SyscallConn returns a raw network connection. This implements the syscall.Conn interface.

func (*UnixConn) Write

func (c *UnixConn) Write(b []byte) (int, error)

Write implements the Conn Write method.

func (*UnixConn) WriteMsgUnix

func (c *UnixConn) WriteMsgUnix(b, oob []byte, addr *UnixAddr) (n, oobn int, err error)

WriteMsgUnix writes a message to addr via c, copying the payload from b and the associated out-of-band data from oob. It returns the number of payload and out-of-band bytes written.

Note that if len(b) == 0 and len(oob) > 0, this function will still write 1 byte to the connection.

func (*UnixConn) WriteTo

func (c *UnixConn) WriteTo(b []byte, addr Addr) (int, error)

WriteTo implements the PacketConn WriteTo method.

func (*UnixConn) WriteToUnix

func (c *UnixConn) WriteToUnix(b []byte, addr *UnixAddr) (int, error)

WriteToUnix acts like UnixConn.WriteTo but takes a UnixAddr.

type UnixListener

type UnixListener struct {
	// contains filtered or unexported fields
}

UnixListener is a Unix domain socket listener. Clients should typically use variables of type Listener instead of assuming Unix domain sockets.

func ListenUnix

func ListenUnix(network string, laddr *UnixAddr) (*UnixListener, error)

ListenUnix acts like Listen for Unix networks.

The network must be "unix" or "unixpacket".

func (*UnixListener) Accept

func (l *UnixListener) Accept() (Conn, error)

Accept implements the Accept method in the Listener interface. Returned connections will be of type *UnixConn.

func (*UnixListener) AcceptUnix

func (l *UnixListener) AcceptUnix() (*UnixConn, error)

AcceptUnix accepts the next incoming call and returns the new connection.

func (*UnixListener) Addr

func (l *UnixListener) Addr() Addr

Addr returns the listener's network address. The Addr returned is shared by all invocations of Addr, so do not modify it.

func (*UnixListener) Close

func (l *UnixListener) Close() error

Close stops listening on the Unix address. Already accepted connections are not closed.

func (*UnixListener) File

func (l *UnixListener) File() (f *os.File, err error)

File returns a copy of the underlying os.File. It is the caller's responsibility to close f when finished. Closing l does not affect f, and closing f does not affect l.

The returned os.File's file descriptor is different from the connection's. Attempting to change properties of the original using this duplicate may or may not have the desired effect.

func (*UnixListener) SetDeadline

func (l *UnixListener) SetDeadline(t time.Time) error

SetDeadline sets the deadline associated with the listener. A zero time value disables the deadline.

func (*UnixListener) SetUnlinkOnClose

func (l *UnixListener) SetUnlinkOnClose(unlink bool)

SetUnlinkOnClose sets whether the underlying socket file should be removed from the file system when the listener is closed.

The default behavior is to unlink the socket file only when package net created it. That is, when the listener and the underlying socket file were created by a call to Listen or ListenUnix, then by default closing the listener will remove the socket file. but if the listener was created by a call to FileListener to use an already existing socket file, then by default closing the listener will not remove the socket file.

func (*UnixListener) SyscallConn

func (l *UnixListener) SyscallConn() (syscall.RawConn, error)

SyscallConn returns a raw network connection. This implements the syscall.Conn interface.

The returned RawConn only supports calling Control. Read and Write return an error.

type UnknownNetworkError

type UnknownNetworkError string

func (UnknownNetworkError) Error

func (e UnknownNetworkError) Error() string

func (UnknownNetworkError) Temporary

func (e UnknownNetworkError) Temporary() bool

func (UnknownNetworkError) Timeout

func (e UnknownNetworkError) Timeout() bool

Directories

http Package http provides HTTP client and server implementations.
mail Package mail implements parsing of mail messages.
netip Package netip defines an IP address type that's a small value type.
rpc Package rpc provides access to the exported methods of an object across a network or other I/O connection.
smtp Package smtp implements the Simple Mail Transfer Protocol as defined in RFC 5321.
textproto Package textproto implements generic support for text-based request/response protocols in the style of HTTP, NNTP, and SMTP.
url Package url parses URLs and implements query escaping.