UDP(4P)
NAME
udp − Internet User Datagram Protocol
USAGE
#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.
DIAGNOSTICS
A udp socket operation may fail with one of the following errors returned:
[EISCONN] An attempt was made to establish a connection on a socket which is already connected, or an attempt was made to send a datagram with the destination address of a connected socket specified.
[ENOTCONN] An attempt was made to send a datagram, but no destination address was specified and the socket hasn’t been connected.
[ENOBUFS] The system can’t allocate enough memory for an internal data structure.
[EADDRINUSE] An attempt was made to create a socket with a port that has already been allocated.
[EADDRNOTAVAIL]
An attempt was made to create a socket with a network address for which no network interface exists.