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Run Format

Package net

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 ▾

Constants
Variables
func InterfaceAddrs() ([]Addr, error)
func Interfaces() ([]Interface, error)
func JoinHostPort(host, port string) string
func LookupAddr(addr string) (names []string, err error)
func LookupCNAME(host string) (cname string, err error)
func LookupHost(host string) (addrs []string, err error)
func LookupIP(host string) ([]IP, error)
func LookupMX(name string) ([]*MX, error)
func LookupNS(name string) ([]*NS, error)
func LookupPort(network, service string) (port int, err error)
func LookupSRV(service, proto, name string) (cname string, addrs []*SRV, err error)
func LookupTXT(name string) ([]string, error)
func SplitHostPort(hostport string) (host, port string, err error)
type Addr
type AddrError
    func (e *AddrError) Error() string
    func (e *AddrError) Temporary() bool
    func (e *AddrError) Timeout() bool
type Buffers
    func (v *Buffers) Read(p []byte) (n int, err error)
    func (v *Buffers) WriteTo(w io.Writer) (n int64, err error)
type Conn
    func Dial(network, address string) (Conn, error)
    func DialTimeout(network, address string, timeout time.Duration) (Conn, error)
    func FileConn(f *os.File) (c Conn, err error)
    func Pipe() (Conn, Conn)
type DNSConfigError
    func (e *DNSConfigError) Error() string
    func (e *DNSConfigError) Temporary() bool
    func (e *DNSConfigError) Timeout() bool
type DNSError
    func (e *DNSError) Error() string
    func (e *DNSError) Temporary() bool
    func (e *DNSError) Timeout() bool
type Dialer
    func (d *Dialer) Dial(network, address string) (Conn, error)
    func (d *Dialer) DialContext(ctx context.Context, network, address string) (Conn, error)
type Error
type Flags
    func (f Flags) String() string
type HardwareAddr
    func ParseMAC(s string) (hw HardwareAddr, err error)
    func (a HardwareAddr) String() string
type IP
    func IPv4(a, b, c, d byte) IP
    func ParseCIDR(s string) (IP, *IPNet, error)
    func ParseIP(s string) IP
    func (ip IP) DefaultMask() IPMask
    func (ip IP) Equal(x IP) bool
    func (ip IP) IsGlobalUnicast() bool
    func (ip IP) IsInterfaceLocalMulticast() bool
    func (ip IP) IsLinkLocalMulticast() bool
    func (ip IP) IsLinkLocalUnicast() bool
    func (ip IP) IsLoopback() bool
    func (ip IP) IsMulticast() bool
    func (ip IP) IsUnspecified() bool
    func (ip IP) MarshalText() ([]byte, error)
    func (ip IP) Mask(mask IPMask) IP
    func (ip IP) String() string
    func (ip IP) To16() IP
    func (ip IP) To4() IP
    func (ip *IP) UnmarshalText(text []byte) error
type IPAddr
    func ResolveIPAddr(net, addr string) (*IPAddr, error)
    func (a *IPAddr) Network() string
    func (a *IPAddr) String() string
type IPConn
    func DialIP(netProto string, laddr, raddr *IPAddr) (*IPConn, error)
    func ListenIP(netProto string, laddr *IPAddr) (*IPConn, error)
    func (c *IPConn) Close() error
    func (c *IPConn) File() (f *os.File, err error)
    func (c *IPConn) LocalAddr() Addr
    func (c *IPConn) Read(b []byte) (int, error)
    func (c *IPConn) ReadFrom(b []byte) (int, Addr, error)
    func (c *IPConn) ReadFromIP(b []byte) (int, *IPAddr, error)
    func (c *IPConn) ReadMsgIP(b, oob []byte) (n, oobn, flags int, addr *IPAddr, err error)
    func (c *IPConn) RemoteAddr() Addr
    func (c *IPConn) SetDeadline(t time.Time) error
    func (c *IPConn) SetReadBuffer(bytes int) error
    func (c *IPConn) SetReadDeadline(t time.Time) error
    func (c *IPConn) SetWriteBuffer(bytes int) error
    func (c *IPConn) SetWriteDeadline(t time.Time) error
    func (c *IPConn) Write(b []byte) (int, error)
    func (c *IPConn) WriteMsgIP(b, oob []byte, addr *IPAddr) (n, oobn int, err error)
    func (c *IPConn) WriteTo(b []byte, addr Addr) (int, error)
    func (c *IPConn) WriteToIP(b []byte, addr *IPAddr) (int, error)
type IPMask
    func CIDRMask(ones, bits int) IPMask
    func IPv4Mask(a, b, c, d byte) IPMask
    func (m IPMask) Size() (ones, bits int)
    func (m IPMask) String() string
type IPNet
    func (n *IPNet) Contains(ip IP) bool
    func (n *IPNet) Network() string
    func (n *IPNet) String() string
type Interface
    func InterfaceByIndex(index int) (*Interface, error)
    func InterfaceByName(name string) (*Interface, error)
    func (ifi *Interface) Addrs() ([]Addr, error)
    func (ifi *Interface) MulticastAddrs() ([]Addr, error)
type InvalidAddrError
    func (e InvalidAddrError) Error() string
    func (e InvalidAddrError) Temporary() bool
    func (e InvalidAddrError) Timeout() bool
type Listener
    func FileListener(f *os.File) (ln Listener, err error)
    func Listen(net, laddr string) (Listener, error)
type MX
type NS
type OpError
    func (e *OpError) Error() string
    func (e *OpError) Temporary() bool
    func (e *OpError) Timeout() bool
type PacketConn
    func FilePacketConn(f *os.File) (c PacketConn, err error)
    func ListenPacket(net, laddr string) (PacketConn, error)
type ParseError
    func (e *ParseError) Error() string
type Resolver
    func (r *Resolver) LookupAddr(ctx context.Context, addr string) (names []string, err error)
    func (r *Resolver) LookupCNAME(ctx context.Context, host string) (cname string, err error)
    func (r *Resolver) LookupHost(ctx context.Context, host string) (addrs []string, err error)
    func (r *Resolver) LookupIPAddr(ctx context.Context, host string) ([]IPAddr, error)
    func (r *Resolver) LookupMX(ctx context.Context, name string) ([]*MX, error)
    func (r *Resolver) LookupNS(ctx context.Context, name string) ([]*NS, error)
    func (r *Resolver) LookupPort(ctx context.Context, network, service string) (port int, err error)
    func (r *Resolver) LookupSRV(ctx context.Context, service, proto, name string) (cname string, addrs []*SRV, err error)
    func (r *Resolver) LookupTXT(ctx context.Context, name string) ([]string, error)
type SRV
type TCPAddr
    func ResolveTCPAddr(net, addr string) (*TCPAddr, error)
    func (a *TCPAddr) Network() string
    func (a *TCPAddr) String() string
type TCPConn
    func DialTCP(net string, laddr, raddr *TCPAddr) (*TCPConn, error)
    func (c *TCPConn) Close() error
    func (c *TCPConn) CloseRead() error
    func (c *TCPConn) CloseWrite() error
    func (c *TCPConn) File() (f *os.File, err error)
    func (c *TCPConn) LocalAddr() Addr
    func (c *TCPConn) Read(b []byte) (int, error)
    func (c *TCPConn) ReadFrom(r io.Reader) (int64, error)
    func (c *TCPConn) RemoteAddr() Addr
    func (c *TCPConn) SetDeadline(t time.Time) error
    func (c *TCPConn) SetKeepAlive(keepalive bool) error
    func (c *TCPConn) SetKeepAlivePeriod(d time.Duration) error
    func (c *TCPConn) SetLinger(sec int) error
    func (c *TCPConn) SetNoDelay(noDelay bool) error
    func (c *TCPConn) SetReadBuffer(bytes int) error
    func (c *TCPConn) SetReadDeadline(t time.Time) error
    func (c *TCPConn) SetWriteBuffer(bytes int) error
    func (c *TCPConn) SetWriteDeadline(t time.Time) error
    func (c *TCPConn) Write(b []byte) (int, error)
type TCPListener
    func ListenTCP(net string, laddr *TCPAddr) (*TCPListener, error)
    func (l *TCPListener) Accept() (Conn, error)
    func (l *TCPListener) AcceptTCP() (*TCPConn, error)
    func (l *TCPListener) Addr() Addr
    func (l *TCPListener) Close() error
    func (l *TCPListener) File() (f *os.File, err error)
    func (l *TCPListener) SetDeadline(t time.Time) error
type UDPAddr
    func ResolveUDPAddr(net, addr string) (*UDPAddr, error)
    func (a *UDPAddr) Network() string
    func (a *UDPAddr) String() string
type UDPConn
    func DialUDP(net string, laddr, raddr *UDPAddr) (*UDPConn, error)
    func ListenMulticastUDP(network string, ifi *Interface, gaddr *UDPAddr) (*UDPConn, error)
    func ListenUDP(net string, laddr *UDPAddr) (*UDPConn, error)
    func (c *UDPConn) Close() error
    func (c *UDPConn) File() (f *os.File, err error)
    func (c *UDPConn) LocalAddr() Addr
    func (c *UDPConn) Read(b []byte) (int, error)
    func (c *UDPConn) ReadFrom(b []byte) (int, Addr, error)
    func (c *UDPConn) ReadFromUDP(b []byte) (int, *UDPAddr, error)
    func (c *UDPConn) ReadMsgUDP(b, oob []byte) (n, oobn, flags int, addr *UDPAddr, err error)
    func (c *UDPConn) RemoteAddr() Addr
    func (c *UDPConn) SetDeadline(t time.Time) error
    func (c *UDPConn) SetReadBuffer(bytes int) error
    func (c *UDPConn) SetReadDeadline(t time.Time) error
    func (c *UDPConn) SetWriteBuffer(bytes int) error
    func (c *UDPConn) SetWriteDeadline(t time.Time) error
    func (c *UDPConn) Write(b []byte) (int, error)
    func (c *UDPConn) WriteMsgUDP(b, oob []byte, addr *UDPAddr) (n, oobn int, err error)
    func (c *UDPConn) WriteTo(b []byte, addr Addr) (int, error)
    func (c *UDPConn) WriteToUDP(b []byte, addr *UDPAddr) (int, error)
type UnixAddr
    func ResolveUnixAddr(net, addr string) (*UnixAddr, error)
    func (a *UnixAddr) Network() string
    func (a *UnixAddr) String() string
type UnixConn
    func DialUnix(net string, laddr, raddr *UnixAddr) (*UnixConn, error)
    func ListenUnixgram(net string, laddr *UnixAddr) (*UnixConn, error)
    func (c *UnixConn) Close() error
    func (c *UnixConn) CloseRead() error
    func (c *UnixConn) CloseWrite() error
    func (c *UnixConn) File() (f *os.File, err error)
    func (c *UnixConn) LocalAddr() Addr
    func (c *UnixConn) Read(b []byte) (int, error)
    func (c *UnixConn) ReadFrom(b []byte) (int, Addr, error)
    func (c *UnixConn) ReadFromUnix(b []byte) (int, *UnixAddr, error)
    func (c *UnixConn) ReadMsgUnix(b, oob []byte) (n, oobn, flags int, addr *UnixAddr, err error)
    func (c *UnixConn) RemoteAddr() Addr
    func (c *UnixConn) SetDeadline(t time.Time) error
    func (c *UnixConn) SetReadBuffer(bytes int) error
    func (c *UnixConn) SetReadDeadline(t time.Time) error
    func (c *UnixConn) SetWriteBuffer(bytes int) error
    func (c *UnixConn) SetWriteDeadline(t time.Time) error
    func (c *UnixConn) Write(b []byte) (int, error)
    func (c *UnixConn) WriteMsgUnix(b, oob []byte, addr *UnixAddr) (n, oobn int, err error)
    func (c *UnixConn) WriteTo(b []byte, addr Addr) (int, error)
    func (c *UnixConn) WriteToUnix(b []byte, addr *UnixAddr) (int, error)
type UnixListener
    func ListenUnix(net string, laddr *UnixAddr) (*UnixListener, error)
    func (l *UnixListener) Accept() (Conn, error)
    func (l *UnixListener) AcceptUnix() (*UnixConn, error)
    func (l *UnixListener) Addr() Addr
    func (l *UnixListener) Close() error
    func (l *UnixListener) File() (f *os.File, err error)
    func (l *UnixListener) SetDeadline(t time.Time) error
    func (l *UnixListener) SetUnlinkOnClose(unlink bool)
type UnknownNetworkError
    func (e UnknownNetworkError) Error() string
    func (e UnknownNetworkError) Temporary() bool
    func (e UnknownNetworkError) Timeout() bool
Bugs

Examples

CIDRMask
Listener

Package files

addrselect.go cgo_linux.go cgo_resnew.go cgo_socknew.go cgo_unix.go conf.go dial.go dnsclient.go dnsclient_unix.go dnsconfig_unix.go dnsmsg.go fd_mutex.go fd_poll_runtime.go fd_posix.go fd_unix.go file.go file_unix.go hook.go hook_cloexec.go hook_unix.go hosts.go interface.go interface_linux.go ip.go iprawsock.go iprawsock_posix.go ipsock.go ipsock_posix.go lookup.go lookup_unix.go mac.go net.go nss.go parse.go pipe.go port.go port_unix.go sendfile_linux.go sock_cloexec.go sock_linux.go sock_posix.go sockopt_linux.go sockopt_posix.go sockoptip_linux.go sockoptip_posix.go tcpsock.go tcpsock_posix.go tcpsockopt_posix.go tcpsockopt_unix.go udpsock.go udpsock_posix.go unixsock.go unixsock_posix.go writev_unix.go

Constants

IP address lengths (bytes).

const (
    IPv4len = 4
    IPv6len = 16
)

Variables

Well-known IPv4 addresses

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 IPv6 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}
)

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

var DefaultResolver = &Resolver{}

Various errors contained in OpError.

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

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.

func Interfaces

func Interfaces() ([]Interface, error)

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

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.

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

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.

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.

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 LookupMX

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

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

func LookupNS

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

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

func LookupPort

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

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

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.

func LookupTXT

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

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

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".

type Addr

Addr represents a network end point address.

The two methods Network and 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.

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")
}

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

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").

type Buffers [][]byte

func (*Buffers) Read

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

func (*Buffers) WriteTo

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

type Conn

Conn is a generic stream-oriented network connection.

Multiple goroutines may invoke methods on a Conn simultaneously.

type Conn interface {
    // Read reads data from the connection.
    // Read can be made to time out and return an 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 an 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 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.
    //
    // 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
}

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.

If the host is resolved to multiple addresses, Dial will try each address in order until one succeeds.

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.

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.

type DNSConfigError

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

type DNSConfigError struct {
    Err error
}

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

DNSError represents a DNS lookup error.

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
}

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

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.

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

    // 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
    // cancelation.
    //
    // Deprecated: Use DialContext instead.
    Cancel <-chan struct{}
}

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.

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.

type Error

An Error represents a network error.

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

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

A HardwareAddr represents a physical hardware address.

type HardwareAddr []byte

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

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.

type IP []byte

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 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 198.0.2.1 and the network 198.0.2.0/24.

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.

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.

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) 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) 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

IPAddr represents the address of an IP end point.

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

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".

Resolving a hostname is not recommended because this returns at most one of its IP addresses.

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

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

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

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

An IP mask is an IP address.

type IPMask []byte

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

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.

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

An IPNet represents an IP network.

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

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

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

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
}

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 (*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 Listener

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

Multiple goroutines may invoke methods on a Listener simultaneously.

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
}

Example

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.

Listening on a hostname is not recommended because this creates a socket for at most one of its IP addresses.

type MX

An MX represents a single DNS MX record.

type MX struct {
    Host string
    Pref uint16
}

type NS

An NS represents a single DNS NS record.

type NS struct {
    Host string
}

type OpError

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

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
}

func (*OpError) Error

func (e *OpError) Error() string

func (*OpError) Temporary

func (e *OpError) Temporary() bool

func (*OpError) Timeout

func (e *OpError) Timeout() bool

type PacketConn

PacketConn is a generic packet-oriented network connection.

Multiple goroutines may invoke methods on a PacketConn simultaneously.

type PacketConn interface {
    // ReadFrom reads a packet from the connection,
    // copying the payload into b. It returns the number of
    // bytes copied into b and the return address that
    // was on the packet.
    // ReadFrom can be made to time out and return
    // an Error with Timeout() == true after a fixed time limit;
    // see SetDeadline and SetReadDeadline.
    ReadFrom(b []byte) (n int, addr Addr, err error)

    // WriteTo writes a packet with payload b to addr.
    // WriteTo 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.
    WriteTo(b []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.
    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 with a timeout (see type Error) instead of
    // blocking. The deadline applies to all future and pending
    // I/O, not just the immediately following call to ReadFrom or
    // WriteTo. After a deadline has been exceeded, the connection
    // can be refreshed by setting a deadline in the future.
    //
    // 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
}

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(net, laddr string) (PacketConn, error)

ListenPacket announces on the local network address laddr. The network net must be a packet-oriented network: "udp", "udp4", "udp6", "ip", "ip4", "ip6" or "unixgram". For TCP and UDP, the syntax of laddr is "host:port", like "127.0.0.1:8080". If host is omitted, as in ":8080", ListenPacket listens on all available interfaces instead of just the interface with the given host address. See Dial for the syntax of laddr.

Listening on a hostname is not recommended because this creates a socket for at most one of its IP addresses.

type ParseError

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

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
}

func (*ParseError) Error

func (e *ParseError) Error() string

type Resolver

A Resolver looks up names and numbers.

A nil *Resolver is equivalent to a zero 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
}

func (*Resolver) LookupAddr

func (r *Resolver) LookupAddr(ctx context.Context, 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 (*Resolver) LookupCNAME

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

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) 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.

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.

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.

func (*Resolver) LookupSRV

func (r *Resolver) LookupSRV(ctx context.Context, 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.

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

An SRV represents a single DNS SRV record.

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

type TCPAddr

TCPAddr represents the address of a TCP end point.

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

func ResolveTCPAddr

func ResolveTCPAddr(net, addr string) (*TCPAddr, error)

ResolveTCPAddr parses addr as a TCP address of the form "host:port" or "[ipv6-host%zone]:port" and resolves a pair of domain name and port name on the network net, which must be "tcp", "tcp4" or "tcp6". 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".

Resolving a hostname is not recommended because this returns at most one of its IP addresses.

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

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

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

func DialTCP

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

DialTCP connects to the remote address raddr on the network net, which must be "tcp", "tcp4", or "tcp6". If laddr is not nil, it is used as the local address for the connection.

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 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 (*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) 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 keepalive 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 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) Write

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

Write implements the Conn Write method.

type TCPListener

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

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

func ListenTCP

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

ListenTCP announces on the TCP address laddr and returns a TCP listener. Net must be "tcp", "tcp4", or "tcp6". If laddr has a port of 0, ListenTCP will choose an available port. The caller can use the Addr method of TCPListener to retrieve the chosen address.

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, set to blocking mode. 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.

type UDPAddr

UDPAddr represents the address of a UDP end point.

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

func ResolveUDPAddr

func ResolveUDPAddr(net, addr string) (*UDPAddr, error)

ResolveUDPAddr parses addr as a UDP address of the form "host:port" or "[ipv6-host%zone]:port" and resolves a pair of domain name and port name on the network net, which must be "udp", "udp4" or "udp6". 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".

Resolving a hostname is not recommended because this returns at most one of its IP addresses.

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

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

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

func DialUDP

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

DialUDP connects to the remote address raddr on the network net, which must be "udp", "udp4", or "udp6". If laddr is not nil, it is used as the local address for the connection.

func ListenMulticastUDP

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

ListenMulticastUDP listens for incoming multicast UDP packets addressed to the group address gaddr on the interface ifi. Network must be "udp", "udp4" or "udp6". ListenMulticastUDP uses the system-assigned multicast interface when ifi is nil, although this is not recommended because the assignment depends on platforms and sometimes it might require routing configuration.

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.

func ListenUDP

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

ListenUDP listens for incoming UDP packets addressed to the local address laddr. Net must be "udp", "udp4", or "udp6". If laddr has a port of 0, ListenUDP will choose an available port. The LocalAddr method of the returned UDPConn can be used to discover the port. The returned connection's ReadFrom and WriteTo methods can be used to receive and send UDP packets with per-packet addressing.

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 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 (*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) (int, *UDPAddr, error)

ReadFromUDP reads a UDP 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.

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

func (*UDPConn) ReadMsgUDP

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

ReadMsgUDP 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 (*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) 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 packet to addr via c if c isn't connected, or to c's remote destination 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.

func (*UDPConn) WriteTo

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

WriteTo implements the PacketConn WriteTo method.

func (*UDPConn) WriteToUDP

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

WriteToUDP writes a UDP packet to addr via c, copying the payload from b.

WriteToUDP 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 UnixAddr

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

type UnixAddr struct {
    Name string
    Net  string
}

func ResolveUnixAddr

func ResolveUnixAddr(net, addr string) (*UnixAddr, error)

ResolveUnixAddr parses addr as a Unix domain socket address. The string net gives the network name, "unix", "unixgram" or "unixpacket".

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

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

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

func DialUnix

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

DialUnix connects to the remote address raddr on the network net, which must be "unix", "unixgram" or "unixpacket". If laddr is not nil, it is used as the local address for the connection.

func ListenUnixgram

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

ListenUnixgram listens for incoming Unix datagram packets addressed to the local address laddr. The network net must be "unixgram". The returned connection's ReadFrom and WriteTo methods can be used to receive and send packets with per-packet addressing.

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 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 (*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 reads a packet from c, copying the payload into b. It returns the number of bytes copied into b and the source address of the packet.

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

func (*UnixConn) ReadMsgUnix

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

ReadMsgUnix 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.

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) 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 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.

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

WriteToUnix 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 UnixListener

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

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

func ListenUnix

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

ListenUnix announces on the Unix domain socket laddr and returns a Unix listener. The network net 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, set to blocking mode. 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.

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

Bugs

Subdirectories

Name Synopsis
..
http Package http provides HTTP client and server implementations.
cgi Package cgi implements CGI (Common Gateway Interface) as specified in RFC 3875.
cookiejar Package cookiejar implements an in-memory RFC 6265-compliant http.CookieJar.
fcgi Package fcgi implements the FastCGI protocol.
httptest Package httptest provides utilities for HTTP testing.
httptrace Package httptrace provides mechanisms to trace the events within HTTP client requests.
httputil Package httputil provides HTTP utility functions, complementing the more common ones in the net/http package.
pprof Package pprof serves via its HTTP server runtime profiling data in the format expected by the pprof visualization tool.
mail Package mail implements parsing of mail messages.
rpc Package rpc provides access to the exported methods of an object across a network or other I/O connection.
jsonrpc Package jsonrpc implements a JSON-RPC ClientCodec and ServerCodec for the rpc package.
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.