V10/man/man3/udp.3

.TH UDP 3X
.CT 2 comm_mach
.SH NAME
udp_connect, udp_listen, udp_datagram \(mi udp networking functions
.SH SYNOPSIS
.nf
.B #include <sys/inet/udp_user.h>
.PP
.B int udp_connect(sport, dhost, dport)
.B in_addr dhost;
.B udp_port sport, dport;
.PP
.B int udp_listen(sport, reply)
.B udp_port sport;
.B struct udpreply *reply;
.PP
.B int 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 (universal datagram protocol) is a protocol 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 file descriptor of a UDP socket bound to port
.I sport.
Each
.IR read (2)
from this file descriptor will only accept datagrams from the UDP
socket at host
.I dhost,
port
.IR dport ;
a
.IR write
on this file descriptor will be sent to that socket.
.PP
.I Udp_listen
returns the file descriptor 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 writes
will go to that socket and
reads will only accept data from that socket.
.PP
.I Udp_datagram
returns the file descriptor of a UDP socket bound to port
.I sport.
Messages written to the file descriptor must start with a
.B struct udpaddr
which contains the destination of the message.
.IP
.EX
.ta \w'struct 'u +\w'updaddr 'u
struct	udpaddr	{
	in_addr	host;
	int	port;
};
.EE
.PP
Messages read from the file descriptor also start with a
.B struct udpaddr
and contain the address of the source socket.
.SH FILES
.TP 12
.F /dev/udp*
the socket devices
.SH SEE ALSO
.IR internet (3), 
.IR tcp (3)
.SH DIAGNOSTICS
All these routines
returns \-1 on failure.