net

package
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 Go to latest Published: Jun 6, 2023 License: BSD-3-Clause Imports: 15 Imported by: 0

Documentation

Overview

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 cgo resolver

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

On Windows, the resolver always uses C library functions, such as GetAddrInfo and DnsQuery.

Index

Examples

Constants

View Source 
const (
	IPv4len = 4
	IPv6len = 16
)

IP address lengths (bytes).

Variables

View Source 
var (
	IPv4bcast     = IPv4(255, 255, 255, 255) // 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

View Source 
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

View Source 
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" or, if host contains a colon or a percent sign, "[host]:port".

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.

func LookupCNAME 

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

LookupCNAME returns the canonical DNS host for the given name. 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.

func LookupHost 

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

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

func LookupPort 

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

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

func LookupTXT 

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

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

func ParseCIDR 

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

ParseCIDR parses s as a CIDR notation IP address and mask, 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 mask. For example, ParseCIDR("198.51.100.1/24") returns the IP address 198.51.100.1 and the network 198.51.100.0/24.

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]:port" or "[ipv6-host%zone]:port" into host or ipv6-host%zone and port. A literal address or host name for IPv6 must be enclosed in square brackets, as in "[::1]:80", "[ipv6-host]:http" or "[ipv6-host%zone]:80".

Types

type Addr 

type Addr interface {
	Network() string // name of the network
	String() string  // string form of address
}

Addr represents a network end point address.

func InterfaceAddrs 

func InterfaceAddrs() ([]Addr, error)

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

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 Conn 

type Conn interface {
	// Read reads data from the connection.
	// Read can be made to time out and return a Error with Timeout() == true
	// 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 a Error with Timeout() == true
	// 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.
	LocalAddr() Addr

	// RemoteAddr returns the remote network address.
	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 with a timeout (see type Error) instead of
	// blocking. The deadline applies to all future I/O, not just
	// the immediately following call to Read or Write.
	//
	// 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.
	// A zero value for t means Read will not time out.
	SetReadDeadline(t time.Time) error

	// SetWriteDeadline sets the deadline for future Write calls.
	// 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, addresses have the form host:port. If host is a literal IPv6 address it must be enclosed in square brackets as in "[::1]:80" or "[ipv6-host%zone]:80". The functions JoinHostPort and SplitHostPort manipulate addresses in this form. If the host is empty, as in ":80", the local system is assumed.

Examples: 

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

For IP networks, the network must be "ip", "ip4" or "ip6" followed by a colon and a protocol number or name and the addr must be a literal IP address.

Examples: 

Dial("ip4:1", "192.0.2.1")
Dial("ip6:ipv6-icmp", "2001:db8::1")

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.

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

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
}

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 dialing a 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 enables RFC 6555-compliant "Happy Eyeballs" dialing
	// when the network is "tcp" and the destination is a host name
	// with both IPv4 and IPv6 addresses. This allows a client to
	// tolerate networks where one address family is silently broken.
	DualStack bool

	// FallbackDelay specifies the length of time to wait before
	// spawning a fallback connection, when DualStack is enabled.
	// If zero, a default delay of 300ms is used.
	FallbackDelay time.Duration

	// KeepAlive specifies the keep-alive period for an active
	// network connection.
	// If zero, keep-alives are not enabled. Network protocols
	// that do not support keep-alives ignore this field.
	KeepAlive time.Duration

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

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.

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.

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.

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

type Error 

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

An Error represents a network error.

type Flags 

type Flags uint
const (
	FlagUp           Flags = 1 << iota // interface is 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
)

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: 

01:23:45:67:89:ab
01:23:45:67:89:ab:cd:ef
01:23:45:67:89:ab:cd:ef:00:00:01:23:45:67:89:ab:cd:ef:00:00
01-23-45-67-89-ab
01-23-45-67-89-ab-cd-ef
01-23-45-67-89-ab-cd-ef-00-00-01-23-45-67-89-ab-cd-ef-00-00
0123.4567.89ab
0123.4567.89ab.cdef
0123.4567.89ab.cdef.0000.0123.4567.89ab.cdef.0000

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.

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.

func LookupIP 

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

LookupIP looks up host using the local resolver. It returns an array 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 dotted decimal ("192.0.2.1") or IPv6 ("2001:db8::68") form. If s is not a valid textual representation of an IP address, ParseIP returns 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.

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.

func (IP) IsGlobalUnicast 

func (ip IP) IsGlobalUnicast() bool

IsGlobalUnicast reports whether ip is a global unicast address.

func (IP) IsInterfaceLocalMulticast 

func (ip IP) IsInterfaceLocalMulticast() bool

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

func (IP) IsLinkLocalMulticast 

func (ip IP) IsLinkLocalMulticast() bool

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

func (IP) IsLinkLocalUnicast 

func (ip IP) IsLinkLocalUnicast() bool

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

func (IP) IsLoopback 

func (ip IP) IsLoopback() bool

IsLoopback reports whether ip is a loopback address.

func (IP) IsMulticast 

func (ip IP) IsMulticast() bool

IsMulticast reports whether ip is a multicast address.

func (IP) IsUnspecified 

func (ip IP) IsUnspecified() bool

IsUnspecified reports whether ip is an unspecified address.

func (IP) MarshalText 

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

MarshalText implements the encoding.TextMarshaler interface. The encoding is the same as returned by String.

func (IP) Mask 

func (ip IP) Mask(mask IPMask) IP

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

func (IP) String 

func (ip IP) String() string

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

  • "<nil>", if ip has length 0
  • dotted decimal ("192.0.2.1"), if ip is an IPv4 or IP4-mapped IPv6 address
  • IPv6 ("2001:db8::1"), if ip is a valid IPv6 address
  • the hexadecimal form of ip, without punctuation, if no other cases apply

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) 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.

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(net, addr string) (*IPAddr, error)

ResolveIPAddr parses addr as an IP address of the form "host" or "ipv6-host%zone" and resolves the domain name on the network net, which must be "ip", "ip4" or "ip6".

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(netProto string, laddr, raddr *IPAddr) (*IPConn, error)

DialIP connects to the remote address raddr on the network protocol netProto, which must be "ip", "ip4", or "ip6" followed by a colon and a protocol number or name.

func ListenIP 

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

ListenIP listens for incoming IP packets addressed to the local address laddr. The returned connection's ReadFrom and WriteTo methods can be used to receive and send IP packets with per-packet addressing.

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 sets the underlying os.File to blocking mode and returns a copy. 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 reads an IP packet from c, copying the payload into b. It returns the number of bytes copied into b and the return address that was on the packet.

ReadFromIP can be made to time out and return an error with Timeout() == true after a fixed time limit; see SetDeadline and SetReadDeadline.

func (*IPConn) ReadMsgIP 

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

ReadMsgIP reads a packet 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 packet and the source address of the packet.

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) 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 packet 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.

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 writes an IP packet to addr via c, copying the payload from b.

WriteToIP can be made to time out and return an error with Timeout() == true after a fixed time limit; see SetDeadline and SetWriteDeadline. On packet-oriented connections, write timeouts are rare.

type IPMask 

type IPMask []byte

An IP mask is an IP address.

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.

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.

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 "192.0.2.1/24" 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 "198.51.100.1/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.

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 interface addresses for a specific interface.

func (*Interface) MulticastAddrs 

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

MulticastAddrs returns 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 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 interfaces.
	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(net, laddr string) (Listener, error)

Listen announces on the local network address laddr. The network net must be a stream-oriented network: "tcp", "tcp4", "tcp6", "unix" or "unixpacket". For TCP and UDP, the syntax of laddr is "host:port", like "127.0.0.1:8080". If host is omitted, as in ":8080", Listen listens on all available interfaces instead of just the interface with the given host address. See Dial for more details about address syntax.

type MX 

type MX struct {
	Host string
	Pref uint16
}

An MX represents a single DNS MX record.

func LookupMX 

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

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

type NS 

type NS struct {
	Host string
}

An NS represents a single DNS NS record.

func LookupNS 

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

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

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.
	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 *