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 sock‐
ets 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(4P).
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 con‐
[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 net‐
work address for which no network interface exists.
getsockopt(2), recv(2), send(2), socket(2), intro(4N), inet(4F), ip(4P)
4.2 Berkeley Distribution May 16, 1986 UDP(4P)