V8/usr/man/man3/udp.3

.TH UDP 3 
.SH NAME
udp_connect, udp_listen, udp_datagram \- udp operations
.SH SYNOPSIS
.nf
.B #include <sys/inet/udp_user.h>
.PP
.B udp_connect(sport, dhost, dport)
.B in_addr dhost;
.B udp_port sport, dport;
.PP
.B udp_listen(sport, reply)
.B udp_port sport;
.B struct udpreply *reply;
.PP
.B udp_datagram(sport)
.B udp_port sport;
.PP
.SH DESCRIPTION
These routines are loaded by the 
.B \-lin
option of
.IR ld (1).
.PP
UDP is one of the many protocols which are layered
upon IP (internet protocol).
It provides datagram service between end points called sockets.
A socket address is composed of the internet address
of its host and the port number to which
the socket is bound.
.PP
.I Udp_connect
returns the fd of a UDP socket bound to port
.I sport.
All 
.IR writes (2)
performed on this fd will be sent to the UDP socket at host
.I dhost,
port
.I dport
and
.IR reads (2)
from this fd will only accept datagrams from that socket.
.I Udp_connect
returns -1 on failure.
.PP
.I Udp_listen
returns the fd of a UDP socket bound to port
.I sport
and waits for a datagram to be sent to that port.
Once a message has been received from another socket,
all
.IR writes (2)
will go to that socket and
.IR reads (2)
will only accept data from that socket.
.PP
.I Udp_datagram
returns the fd of a UDP socket bound to port
.I sport.
All messages written to the socket must start with a
.B struct udpaddr
which contains the destination of the message.
.nf
.I	struct udpaddr {	/* from udp_user.h */
.I		in_addr	host;
.I		int port;
.I	};
.fi
All messages read from the socket also start with a
.B struct udpaddr
and contain the address of the source socket.
.SH FILES
.nf
/dev/udp*	the socket devices
.SH SEE ALSO
internet(3), tcp(3)