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Source file src/net/udpsock.go

Documentation: net

  // Copyright 2009 The Go Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style
  // license that can be found in the LICENSE file.
  
  package net
  
  import (
  	"context"
  	"syscall"
  )
  
  // BUG(mikio): On NaCl, Plan 9 and Windows, the ReadMsgUDP and
  // WriteMsgUDP methods of UDPConn are not implemented.
  
  // BUG(mikio): On Windows, the File method of UDPConn is not
  // implemented.
  
  // BUG(mikio): On NaCl, the ListenMulticastUDP function is not
  // implemented.
  
  // UDPAddr represents the address of a UDP end point.
  type UDPAddr struct {
  	IP   IP
  	Port int
  	Zone string // IPv6 scoped addressing zone
  }
  
  // Network returns the address's network name, "udp".
  func (a *UDPAddr) Network() string { return "udp" }
  
  func (a *UDPAddr) 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 *UDPAddr) isWildcard() bool {
  	if a == nil || a.IP == nil {
  		return true
  	}
  	return a.IP.IsUnspecified()
  }
  
  func (a *UDPAddr) opAddr() Addr {
  	if a == nil {
  		return nil
  	}
  	return a
  }
  
  // ResolveUDPAddr returns an address of UDP end point.
  //
  // The network must be a UDP network name.
  //
  // If the host in the address parameter is not a literal IP address or
  // the port is not a literal port number, ResolveUDPAddr resolves the
  // address to an address of UDP end point.
  // Otherwise, it parses the address as a pair of literal IP address
  // and port number.
  // The address parameter can use a host name, but this is not
  // recommended, because it will return at most one of the host name's
  // IP addresses.
  //
  // See func Dial for a description of the network and address
  // parameters.
  func ResolveUDPAddr(network, address string) (*UDPAddr, error) {
  	switch network {
  	case "udp", "udp4", "udp6":
  	case "": // a hint wildcard for Go 1.0 undocumented behavior
  		network = "udp"
  	default:
  		return nil, UnknownNetworkError(network)
  	}
  	addrs, err := DefaultResolver.internetAddrList(context.Background(), network, address)
  	if err != nil {
  		return nil, err
  	}
  	return addrs.forResolve(network, address).(*UDPAddr), nil
  }
  
  // UDPConn is the implementation of the Conn and PacketConn interfaces
  // for UDP network connections.
  type UDPConn struct {
  	conn
  }
  
  // SyscallConn returns a raw network connection.
  // This implements the syscall.Conn interface.
  func (c *UDPConn) SyscallConn() (syscall.RawConn, error) {
  	if !c.ok() {
  		return nil, syscall.EINVAL
  	}
  	return newRawConn(c.fd)
  }
  
  // ReadFromUDP acts like ReadFrom but returns a UDPAddr.
  func (c *UDPConn) ReadFromUDP(b []byte) (int, *UDPAddr, error) {
  	if !c.ok() {
  		return 0, nil, syscall.EINVAL
  	}
  	n, addr, err := c.readFrom(b)
  	if err != nil {
  		err = &OpError{Op: "read", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
  	}
  	return n, addr, err
  }
  
  // ReadFrom implements the PacketConn ReadFrom method.
  func (c *UDPConn) ReadFrom(b []byte) (int, Addr, error) {
  	if !c.ok() {
  		return 0, nil, syscall.EINVAL
  	}
  	n, addr, err := c.readFrom(b)
  	if err != nil {
  		err = &OpError{Op: "read", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
  	}
  	if addr == nil {
  		return n, nil, err
  	}
  	return n, addr, err
  }
  
  // ReadMsgUDP reads a message from c, copying the payload into b and
  // the associated out-of-band data into oob. It returns the number of
  // bytes copied into b, the number of bytes copied into oob, the flags
  // that were set on the message and the source address of the message.
  //
  // The packages golang.org/x/net/ipv4 and golang.org/x/net/ipv6 can be
  // used to manipulate IP-level socket options in oob.
  func (c *UDPConn) ReadMsgUDP(b, oob []byte) (n, oobn, flags int, addr *UDPAddr, err error) {
  	if !c.ok() {
  		return 0, 0, 0, nil, syscall.EINVAL
  	}
  	n, oobn, flags, addr, err = c.readMsg(b, oob)
  	if err != nil {
  		err = &OpError{Op: "read", Net: c.fd.net, Source: c.fd.laddr, Addr: c.fd.raddr, Err: err}
  	}
  	return
  }
  
  // WriteToUDP acts like WriteTo but takes a UDPAddr.
  func (c *UDPConn) WriteToUDP(b []byte, addr *UDPAddr) (int, error) {
  	if !c.ok() {
  		return 0, syscall.EINVAL
  	}
  	n, err := c.writeTo(b, addr)
  	if err != nil {
  		err = &OpError{Op: "write", Net: c.fd.net, Source: c.fd.laddr, Addr: addr.opAddr(), Err: err}
  	}
  	return n, err
  }
  
  // WriteTo implements the PacketConn WriteTo method.
  func (c *UDPConn) WriteTo(b []byte, addr Addr) (int, error) {
  	if !c.ok() {
  		return 0, syscall.EINVAL
  	}
  	a, ok := addr.(*UDPAddr)
  	if !ok {
  		return 0, &OpError{Op: "write", Net: c.fd.net, Source: c.fd.laddr, Addr: addr, Err: syscall.EINVAL}
  	}
  	n, err := c.writeTo(b, a)
  	if err != nil {
  		err = &OpError{Op: "write", Net: c.fd.net, Source: c.fd.laddr, Addr: a.opAddr(), Err: err}
  	}
  	return n, err
  }
  
  // WriteMsgUDP writes a message to addr via c if c isn't connected, or
  // to c's remote address if c is connected (in which case addr must be
  // nil). The payload is copied from b and the associated out-of-band
  // data is copied from oob. It returns the number of payload and
  // out-of-band bytes written.
  //
  // The packages golang.org/x/net/ipv4 and golang.org/x/net/ipv6 can be
  // used to manipulate IP-level socket options in oob.
  func (c *UDPConn) WriteMsgUDP(b, oob []byte, addr *UDPAddr) (n, oobn int, err error) {
  	if !c.ok() {
  		return 0, 0, syscall.EINVAL
  	}
  	n, oobn, err = c.writeMsg(b, oob, addr)
  	if err != nil {
  		err = &OpError{Op: "write", Net: c.fd.net, Source: c.fd.laddr, Addr: addr.opAddr(), Err: err}
  	}
  	return
  }
  
  func newUDPConn(fd *netFD) *UDPConn { return &UDPConn{conn{fd}} }
  
  // DialUDP acts like Dial for UDP networks.
  //
  // The network must be a UDP network name; see func Dial for details.
  //
  // If laddr is nil, a local address is automatically chosen.
  // If the IP field of raddr is nil or an unspecified IP address, the
  // local system is assumed.
  func DialUDP(network string, laddr, raddr *UDPAddr) (*UDPConn, error) {
  	switch network {
  	case "udp", "udp4", "udp6":
  	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}
  	}
  	c, err := dialUDP(context.Background(), network, laddr, raddr)
  	if err != nil {
  		return nil, &OpError{Op: "dial", Net: network, Source: laddr.opAddr(), Addr: raddr.opAddr(), Err: err}
  	}
  	return c, nil
  }
  
  // ListenUDP acts like ListenPacket for UDP networks.
  //
  // The network must be a UDP network name; see func Dial for details.
  //
  // If the IP field of laddr is nil or an unspecified IP address,
  // ListenUDP listens on all available IP addresses of the local system
  // except multicast IP addresses.
  // If the Port field of laddr is 0, a port number is automatically
  // chosen.
  func ListenUDP(network string, laddr *UDPAddr) (*UDPConn, error) {
  	switch network {
  	case "udp", "udp4", "udp6":
  	default:
  		return nil, &OpError{Op: "listen", Net: network, Source: nil, Addr: laddr.opAddr(), Err: UnknownNetworkError(network)}
  	}
  	if laddr == nil {
  		laddr = &UDPAddr{}
  	}
  	c, err := listenUDP(context.Background(), network, laddr)
  	if err != nil {
  		return nil, &OpError{Op: "listen", Net: network, Source: nil, Addr: laddr.opAddr(), Err: err}
  	}
  	return c, nil
  }
  
  // ListenMulticastUDP acts like ListenPacket for UDP networks but
  // takes a group address on a specific network interface.
  //
  // The network must be a UDP network name; see func Dial for details.
  //
  // ListenMulticastUDP listens on all available IP addresses of the
  // local system including the group, multicast IP address.
  // If ifi is nil, ListenMulticastUDP uses the system-assigned
  // multicast interface, although this is not recommended because the
  // assignment depends on platforms and sometimes it might require
  // routing configuration.
  // If the Port field of gaddr is 0, a port number is automatically
  // chosen.
  //
  // ListenMulticastUDP is just for convenience of simple, small
  // applications. There are golang.org/x/net/ipv4 and
  // golang.org/x/net/ipv6 packages for general purpose uses.
  func ListenMulticastUDP(network string, ifi *Interface, gaddr *UDPAddr) (*UDPConn, error) {
  	switch network {
  	case "udp", "udp4", "udp6":
  	default:
  		return nil, &OpError{Op: "listen", Net: network, Source: nil, Addr: gaddr.opAddr(), Err: UnknownNetworkError(network)}
  	}
  	if gaddr == nil || gaddr.IP == nil {
  		return nil, &OpError{Op: "listen", Net: network, Source: nil, Addr: gaddr.opAddr(), Err: errMissingAddress}
  	}
  	c, err := listenMulticastUDP(context.Background(), network, ifi, gaddr)
  	if err != nil {
  		return nil, &OpError{Op: "listen", Net: network, Source: nil, Addr: gaddr.opAddr(), Err: err}
  	}
  	return c, nil
  }
  

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