.TH DIAL 2
.SH NAME
dial, hangup, announce, listen, accept, reject, netmkaddr \- make and break network connections
.SH SYNOPSIS
.B
int	dial(char *addr, char *local, char *dir, int *cfdp)
.PP
.B
int	hangup(int ctl)
.PP
.B
int	announce(char *addr, char *dir)
.PP
.B
int	listen(char *dir, char *newdir)
.PP
.B
int	accept(int ctl, char *dir)
.PP
.B
int	reject(int ctl, char *dir, char *cause)
.PP
.B
char*	netmkaddr(char *addr, char *defnet, char *defservice)
.SH DESCRIPTION
For these routines,
.I addr
is a network address of the form
.IB network ! netaddr ! service,
.IB network ! netaddr,
or simply
.I netaddr.
.I Network
is any directory listed in 
.B /net
or the special token,
.BR net .
.B Net
is a free variable that stands for any network in common
between the source and the host
.IR netaddr .
.I Netaddr
can be a host name, a domain name, a network address,
or a meta-name of the form
.BI $ attribute.
.BI $ attribute
is replaced by
.I value
from the value-attribute pair
.IB attribute = value
most closely associated with the source host in the
network data base (see
.IR ndb (6)).
.PP
If a connection attempt is successful and
.I dir
is non-zero,
the path name of a
.I line directory
that has files for accessing the connection
is copied into
.IR dir .
The path name is guaranteed to be less than 40
bytes long.
One line directory exists for each possible connection.
The
.B data
file in the line directory should be used to communicate with the destination.
The
.B ctl
file in the line directory can be used to send commands to the line.
See
.IR dk (3)
and
.IR ip (3)
for messages that can be written to the
.B ctl
file.
The last close of the
.B data
or
.B ctl
file will close the connection.
.PP
.I Dial
makes a call to destination
.I addr
on a multiplexed network.
If the network in
.I addr
is
.BR net ,
.I dial
will try in succession all
networks in common between source and destination
until a call succeeds.
It returns a file descriptor open for reading and writing the
.B data
file in the line directory.
The
.B addr
file in the line directory contains the address called.
If the network allows the local address to be set,
as is the case with UDP and TCP port numbers, and
.IR local
is non-zero, the local address will be set to
.IR local .
If
.I cfdp
is non-zero,
.BI * cfdp
is set to a file descriptor open for reading and
writing the control file.
.PP
.I Hangup
is a means of forcing a connection to hang up without
closing the
.B ctl
and
.B data
files.
.P
.I Announce
and
.I listen
are the complements of
.I dial.
.I Announce
establishes a network
name to which calls can be made.
Like
.IR dial ,
.I announce
returns an open
.B ctl
file.
The
.I listen
routine takes as its first argument the
.I dir
of a previous
.I announce.
When a call is received,
.I listen
returns an open
.B ctl
file for the line the call was received on.
It sets
.I newdir
to the path name of the new line directory.
.I Accept
accepts a call received by
.IR listen ,
while
.I reject
refuses the call because of
.IR cause .
.I Accept
returns a file descriptor for the data file opened
.B ORDWR .
.PP
.I Netmkaddr
make an address suitable for dialing or announcing.
It takes an address along with a default network and service to use
if they are not specified in the address.
It returns a pointer to static data holding the actual address to use.
.SH EXAMPLES
Make a call and return an open file descriptor to
use for communications:
.IP
.EX
int callkremvax(void)
{
	return dial("kremvax", 0, 0, 0);
}
.EE
.PP
Call the local authentication server:
.IP
.EX
int dialauth(char *service)
{
	return dial(netmkaddr("$auth", 0, service), 0, 0, 0);
}
.EE
.PP
Announce as
.B kremvax
on Datakit and
loop forever receiving calls and echoing back
to the caller anything sent:
.IP
.EX
int
bekremvax(void)
{
	int dfd, acfd, lcfd;
	char adir[40], ldir[40];
	int n;
	char buf[256];

	afd = announce("dk!kremvax", adir);
	if(afd < 0)
		return -1;

	for(;;){
		/* listen for a call */
		lcfd = listen(adir, ldir);
		if(lcfd < 0)
			return -1;

		/* fork a process to echo */
		switch(fork()){
		case -1:
			perror("forking");
			close(lcfd);
			break;
		case 0:
			/* accept the call and open the data file */
			dfd = accept(lcfd, ldir);
			if(dfd < 0)
				return -1;

			/* echo until EOF */
			while((n = read(dfd, buf, sizeof(buf))) > 0)
				write(dfd, buf, n);
			exits(0);
		default:
			close(lcfd);
			break;
		}

	}
}
.EX
.SH "SEE ALSO"
.IR auth (2),
.IR dk (3),
.IR ip (3),
.IR stream (3),
.IR ndb (8)
.SH DIAGNOSTICS
.I Dial,
.I announce,
and
.I listen
return \(mi1 if they fail.
.I Hangup
returns nonzero if it fails.