Source: tcpsock.go in package net


package net

import (
	"context"
	"io"
	"os"
	"syscall"
	"time"
)

BUG(mikio): On JS and Windows, the File method of TCPConn and TCPListener is not implemented.

TCPAddr represents the address of a TCP end point.

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

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

func (a *TCPAddr) Network() string { return "tcp" }

func (a *TCPAddr) String() string {
	if a == nil {
		return "<nil>"
	}
	ip := ipEmptyString(a.IP)
	if a.Zone != "" {
		return JoinHostPort(ip+"%"+a.Zone, itoa(a.Port))
	}
	return JoinHostPort(ip, itoa(a.Port))
}

func (a *TCPAddr) isWildcard() bool {
	if a == nil || a.IP == nil {
		return true
	}
	return a.IP.IsUnspecified()
}

func (a *TCPAddr) opAddr() Addr {
	if a == nil {
		return nil
	}
	return a
}

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

func ResolveTCPAddr(network, address string) (*TCPAddr, error) {
	switch network {
	case "tcp", "tcp4", "tcp6":
	case "": // a hint wildcard for Go 1.0 undocumented behavior
		network = "tcp"
	default:
		return nil, UnknownNetworkError(network)
	}
	addrs, err := DefaultResolver.internetAddrList(context.Background(), network, address)
	if err != nil {
		return nil, err
	}
	return addrs.forResolve(network, address).(*TCPAddr), nil
}

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

type TCPConn struct {
	conn
}

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

func (c *TCPConn) SyscallConn() (syscall.RawConn, error) {
	if !c.ok() {
		return nil, syscall.EINVAL
	}
	return newRawConn(c.fd)
}

ReadFrom implements the io.ReaderFrom ReadFrom method.

func (c *TCPConn) ReadFrom(r io.Reader) (int64, error) {
	if !c.ok() {
		return 0, syscall.EINVAL
	}
	n, err := c.readFrom(r)
	if err != nil && err != io.EOF {
		err = &OpError{Op: "readfrom", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
	}
	return n, err
}

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

func (c *TCPConn) CloseRead() error {
	if !c.ok() {
		return syscall.EINVAL
	}
	if err := c.fd.closeRead(); err != nil {
		return &OpError{Op: "close", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
	}
	return nil
}

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

func (c *TCPConn) CloseWrite() error {
	if !c.ok() {
		return syscall.EINVAL
	}
	if err := c.fd.closeWrite(); err != nil {
		return &OpError{Op: "close", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
	}
	return nil
}

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 (c *TCPConn) SetLinger(sec int) error {
	if !c.ok() {
		return syscall.EINVAL
	}
	if err := setLinger(c.fd, sec); err != nil {
		return &OpError{Op: "set", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
	}
	return nil
}

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

func (c *TCPConn) SetKeepAlive(keepalive bool) error {
	if !c.ok() {
		return syscall.EINVAL
	}
	if err := setKeepAlive(c.fd, keepalive); err != nil {
		return &OpError{Op: "set", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
	}
	return nil
}

SetKeepAlivePeriod sets period between keep-alives.

func (c *TCPConn) SetKeepAlivePeriod(d time.Duration) error {
	if !c.ok() {
		return syscall.EINVAL
	}
	if err := setKeepAlivePeriod(c.fd, d); err != nil {
		return &OpError{Op: "set", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
	}
	return nil
}

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 (c *TCPConn) SetNoDelay(noDelay bool) error {
	if !c.ok() {
		return syscall.EINVAL
	}
	if err := setNoDelay(c.fd, noDelay); err != nil {
		return &OpError{Op: "set", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
	}
	return nil
}

func newTCPConn(fd *netFD) *TCPConn {
	c := &TCPConn{conn{fd}}
	setNoDelay(c.fd, true)
	return c
}

DialTCP acts like Dial for TCP networks. The network must be a TCP network name; see func Dial for details. If laddr is nil, a local address is automatically chosen. If the IP field of raddr is nil or an unspecified IP address, the local system is assumed.

func DialTCP(network string, laddr, raddr *TCPAddr) (*TCPConn, error) {
	switch network {
	case "tcp", "tcp4", "tcp6":
	default:
		return nil, &OpError{Op: "dial", Net: network, Source: laddr.opAddr(), Addr: raddr.opAddr(), Err: UnknownNetworkError(network)}
	}
	if raddr == nil {
		return nil, &OpError{Op: "dial", Net: network, Source: laddr.opAddr(), Addr: nil, Err: errMissingAddress}
	}
	sd := &sysDialer{network: network, address: raddr.String()}
	c, err := sd.dialTCP(context.Background(), laddr, raddr)
	if err != nil {
		return nil, &OpError{Op: "dial", Net: network, Source: laddr.opAddr(), Addr: raddr.opAddr(), Err: err}
	}
	return c, nil
}

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

type TCPListener struct {
	fd *netFD
	lc ListenConfig
}

SyscallConn returns a raw network connection. This implements the syscall.Conn interface. The returned RawConn only supports calling Control. Read and Write return an error.

func (l *TCPListener) SyscallConn() (syscall.RawConn, error) {
	if !l.ok() {
		return nil, syscall.EINVAL
	}
	return newRawListener(l.fd)
}

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

func (l *TCPListener) AcceptTCP() (*TCPConn, error) {
	if !l.ok() {
		return nil, syscall.EINVAL
	}
	c, err := l.accept()
	if err != nil {
		return nil, &OpError{Op: "accept", Net: l.fd.net, Source: nil, Addr: l.fd.laddr, Err: err}
	}
	return c, nil
}

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

func (l *TCPListener) Accept() (Conn, error) {
	if !l.ok() {
		return nil, syscall.EINVAL
	}
	c, err := l.accept()
	if err != nil {
		return nil, &OpError{Op: "accept", Net: l.fd.net, Source: nil, Addr: l.fd.laddr, Err: err}
	}
	return c, nil
}

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

func (l *TCPListener) Close() error {
	if !l.ok() {
		return syscall.EINVAL
	}
	if err := l.close(); err != nil {
		return &OpError{Op: "close", Net: l.fd.net, Source: nil, Addr: l.fd.laddr, Err: err}
	}
	return nil
}

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 (l *TCPListener) Addr() Addr { return l.fd.laddr }

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

func (l *TCPListener) SetDeadline(t time.Time) error {
	if !l.ok() {
		return syscall.EINVAL
	}
	if err := l.fd.pfd.SetDeadline(t); err != nil {
		return &OpError{Op: "set", Net: l.fd.net, Source: nil, Addr: l.fd.laddr, Err: err}
	}
	return nil
}

File returns a copy of the underlying os.File. It is the caller's responsibility to close f when finished. Closing l does not affect f, and closing f does not affect l. The returned os.File's file descriptor is different from the connection's. Attempting to change properties of the original using this duplicate may or may not have the desired effect.

func (l *TCPListener) File() (f *os.File, err error) {
	if !l.ok() {
		return nil, syscall.EINVAL
	}
	f, err = l.file()
	if err != nil {
		return nil, &OpError{Op: "file", Net: l.fd.net, Source: nil, Addr: l.fd.laddr, Err: err}
	}
	return
}

ListenTCP acts like Listen for TCP networks. The network must be a TCP network name; see func Dial for details. If the IP field of laddr is nil or an unspecified IP address, ListenTCP listens on all available unicast and anycast IP addresses of the local system. If the Port field of laddr is 0, a port number is automatically chosen.

func ListenTCP(network string, laddr *TCPAddr) (*TCPListener, error) {
	switch network {
	case "tcp", "tcp4", "tcp6":
	default:
		return nil, &OpError{Op: "listen", Net: network, Source: nil, Addr: laddr.opAddr(), Err: UnknownNetworkError(network)}
	}
	if laddr == nil {
		laddr = &TCPAddr{}
	}
	sl := &sysListener{network: network, address: laddr.String()}
	ln, err := sl.listenTCP(context.Background(), laddr)
	if err != nil {
		return nil, &OpError{Op: "listen", Net: network, Source: nil, Addr: laddr.opAddr(), Err: err}
	}
	return ln, nil
}

roundDurationUp rounds d to the next multiple of to.

func roundDurationUp(d time.Duration, to time.Duration) time.Duration {
	return (d + to - 1) / to