2.11BSD#431 - /usr/man/cat4/udp.0

UDP(4P)             UNIX Programmer's Manual		  UDP(4P)


NAME
     udp - Internet User Datagram Protocol

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

     s = socket(AF_INET, SOCK_DGRAM, 0);

DESCRIPTION
     UDP is a simple, unreliable datagram protocol which is used
     to support the SOCK_DGRAM abstraction for the Internet pro-
     tocol family.  UDP sockets are connectionless, and are nor-
     mally used with the sendto and recvfrom calls, though the
     connect(2) call may also be used to fix the destination for
     future packets (in which case the recv(2) or read(2) and
     send(2) or write(2) system calls 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 (i.e. a UDP port
     may not be "connected" to a TCP port).  In addition broad-
     cast 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
     ip(4P).

DIAGNOSTICS
     A socket operation may fail with one of the following errors
     returned:

     [EISCONN]	    when trying to establish a connection on a
		    socket which already has one, or when trying
		    to send a datagram with the destination
		    address specified and the socket is already
		    connected;

     [ENOTCONN]     when trying to send a datagram, but no desti-
		    nation address is specified, and the socket
		    hasn't been connected;

     [ENOBUFS]	    when the system runs out of memory for an
		    internal data structure;

     [EADDRINUSE]   when an attempt is made to create a socket
		    with a port which has already been allocated;

     [EADDRNOTAVAIL]
		    when an attempt is made to create a socket


Printed 11/26/99	  May 16, 1986				1


UDP(4P)             UNIX Programmer's Manual		  UDP(4P)


		    with a network address for which no network
		    interface exists.

SEE ALSO
     getsockopt(2), recv(2), send(2), socket(2), intro(4N),
     inet(4F), ip(4P)


Printed 11/26/99	  May 16, 1986				2