udp(7)udp(7)NAMEudp - Internet user datagram protocol (UDP)
SYNOPSIS
#include <sys/socket.h> #include <netinet/in.h>
The following is the socket call for AF_INET sockets:
s = socket(AF_INET, SOCK_DGRAM, 0);
The following is the socket call for AF_INET6 sockets:
s = socket(AF_INET6, SOCK_DGRAM, 0);
DESCRIPTION
UDP is a simple, unreliable datagram protocol that 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() functions, though the connect() function may also be used to
fix the destination for future packets, in which case the recv() or
read() and send() or write() functions 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, IPv4 broadcast packets may be sent (assuming the underly‐
ing network supports this) by using a reserved “broadcast address”;
this address is network interface dependent.
Note
There is no broadcast address in IPv6.
Options at the IP transport level may be used with UDP; see the ip(7)
reference page.
ERRORS
If a socket operation fails, errno may be set to one of the following
values: An attempt was made to create a socket with a port that has
already been allocated. An attempt was made to create a socket with a
network address for which no network interface exists. The socket is
already connected. This error occurs when trying to establish connec‐
tion on a socket or when trying to send a datagram with the destination
address specified. The system ran out of memory for an internal data
structure. The destination address of a datagram was not specified,
and the socket has not been connected.
SEE ALSO
Functions: getsockopt(2), recv(2), send(2), socket(2)
Files: netintro(7), inet(7), ip(7)udp(7)
