udp - Internet User Datagram Protocol
s = socket(AF_INET, SOCK_DGRAM, 0);
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 rea
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.
Options at the IP transport level may be used with UDP; see ip(7P).
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
[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
[EADDRINUSE] when an attempt is made to create a socket with a port
which has already been allocated;
when an attempt is made to create a socket with a network
address for which no network interface exists.
getsockopt(2), recv(2), send(2), socket(2), intro(3), inet(7F), ip(7P),
IRIX Network Programming Guide
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