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 _s_e_n_d_t_o and _r_e_c_v_f_r_o_m calls, though the
     _c_o_n_n_e_c_t(2) call may also be used to fix the destination for
     future packets (in which case the _r_e_c_v(2) or _r_e_a_d(2) and
     _s_e_n_d(2) or _w_r_i_t_e(_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
     _i_p(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