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 protocol
family. 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). 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 ip(4).

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(4), inet(4),
ip(4)