UDP(7P)                                                                UDP(7P)


NAME
     udp - Internet User Datagram Protocol

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

     s = socket(AF_INET, SOCK_DGRAM, 0);

     s = socket(AF_INET6, SOCK_DGRAM, 0);

DESCRIPTION
     UDP is a simple, unreliable datagram protocol which is used to support
     the SOCK_DGRAM abstraction for version 4 and version 6 of the Internet
     protocol families.  UDP sockets are connectionless, and are normally 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).

     When binding a UDP socket, if the local port is unspecified (i.e., set to
     0), the system will choose an appropriate port number for it.  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 and applies only to version 4 of the Internet
     protocols.  A similar result can be achieved with IPv6 by using the all
     nodes multicast address.

     Options at the IPv4 (for AF_INET sockets) or IPv6 (for AF_INET6 sockets)
     network level may be used with UDP; see ip(7P).  and ip6(7P).

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 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
                    which has already been allocated;


     [EADDRNOTAVAIL]
                    when an attempt is made to create a socket with a network
                    address for which no network interface exists.

SEE ALSO
     getsockopt(2), recv(2), send(2), socket(2), intro(3), inet(7F),
     inet6(7F), ip(7P), ip6(7P), tcp(7P)
     IRIX Network Programming Guide


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