NAME

udp − Internet User Datagram Protocol

SYNOPSIS

#include <sys/socket.h>
#include <netinet/in.h>
struct sockproto proto = { PF_INET, IPPROTO_UDP };
socket(SOCK_DGRAM, &proto, address, options);
struct sockaddr_in *address; int options;

DESCRIPTION

UDP is a simple, unreliable datagram protocol that supports the SOCK_DGRAM abstraction for the Internet protocol family.  UDP sockets are connectionless and normally use send(3N) and receive(3N) calls.  The destination for future packets can be set via a connect(3N) call.  Then read(2) and write(2) system calls can be used. 

UDP address formats are identical to those used for TCP.  UDP provides a port identifier in addition to the normal Internet address format.  UDP port space is not part of TCP port space (that is, a UDP port cannot be "connected" to a TCP port). 

DIAGNOSTICS

EISCONN
Trying to establish a connection on an already-connected socket, or trying to send a datagram with a destination address and the socket is already connected

ENOTCONN
Trying to send a datagram, but no destination address is specified and the socket hasn’t been connected

ENOBUFS
The system does not have enough memory for an internal data structure

EADDRINUSE
Attempted to create a socket with a port that is allocated

EADDRNOTAVAIL
Attempted to create a socket with an invalid network interface

SEE ALSO

net(7P), inet(7P)

Version 2.4  —  May 08, 1986