udp(5P)                                                   udp(5P)



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 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 calls, though the
     connect(2N) call may also be used to fix the destination for
     future packets (in which case the recv(2N) or send(2N)
     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 (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.

STATUS MESSAGES AND VALUES
     A socket operation may fail with one of the following errors
     returned:

     EISCONN
          when trying to establish a connection on a socket that
          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 destination
          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
          that has already been allocated;

     EADDRNOTAVAIL
          when an attempt is made to create a socket with a



January 1992                                                    1

udp(5P)                                                   udp(5P)



          network address for which no network interface exists.

SEE ALSO
     send(2N), recv(2N), intro(5), inet(5F)



















































2                                                    January 1992