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udp(7)
NAME
  udp - Internet user datagram protocol (UDP)

SYNOPSIS
  #include <sys/socket.h>
  #include <netinet/in.h>

  s = socket(AF_INET, SOCK_DGRAM, 0);

DESCRIPTION
  UDP is a simple, unreliable datagram protocol that is used to support the
  SOCK_DGRAM abstraction for the Internet Protocol family.  UDP sockets are
  connectionless, and are normally used with the sendto() and recvfrom()
  functions, though the connect() function may also be used to fix the
  destination for future packets, in which case the recv() or read() and
  send() or write() functions may be used.

  UDP address formats are identical to those used by TCP.  In particular, UDP
  provides a port identifier in addition to the normal Internet address
  format.  Note that the UDP port space is separate from the TCP port space
  (that is, a UDP port may not be "connected" to a TCP port).  In addition,
  broadcast packets may be sent (assuming the underlying network supports
  this) by using a reserved "broadcast address"; this address is network
  interface dependent.

  Options at the IP transport level may be used with UDP; see the ip()
  reference page.

ERRORS
  If a socket operation fails, errno may be set to one of the following
  values:

  [EISCONN]
  The socket is already connected.  This error occurs when trying to
  establish connection on a socket or when trying to send a datagram with the
  destination address specified.

  [ENOTCONN]
  The destination address of a datagram was not specified, and the socket has
  not been connected.

  [ENOBUFS]
  The system ran out of memory for an internal data structure.

  [EADDRINUSE]
  An attempt was made to create a socket with a port that has already been
  allocated.

  [EADDRNOTAVAIL]
  An attempt was made to create a socket with a network address for which no
  network interface exists.

RELATED INFORMATION
  Functions: getsockopt(2), recv(2), send(2), socket(2)

  Files: netintro(7), inet(7), ip(7)