.TH DIAL 3
.SH NAME
dial, announce, listen, accept, reject, netmkaddr, dialparse \- make and break network connections
.SH SYNOPSIS
.B #include <u.h>
.br
.B #include <libc.h>
.PP
.B
int   dial(char *addr, char *local, char *dir, int *cfdp)
.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)
.\" .PP
.\" .B
.\" void  setnetmtpt(char *to, int tolen, char *from)
.\" .PP
.\" .B
.\" NetConnInfo*  getnetconninfo(char *conndir, int fd)
.\" .PP
.\" .B
.\" void freenetconninfo(NetConnINfo*)
.PP
.B
int   dialparse(char *addr, char **net, char **unix,
.br
.B
          u32int *host, int *port)
.SH DESCRIPTION
For these routines,
.I addr
is a network address of the form
.IB network ! netaddr ! service\f1,
.IB network ! netaddr\f1,
or simply
.IR netaddr .
.I Network
is
.BR tcp ,
.BR udp ,
.BR unix ,
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, or a network address.
.\" or a meta-name of the form
.\" .BI $ attribute\f1,
.\" which
.\" 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
On Plan 9, the
.I dir
argument is a path name to a
.I line directory
that has files for accessing the connection.
To keep the same function signatures,
the Unix port of these routines uses strings of the form
.BI /dev/fd/ n
instead of line directory paths.
These strings should be treated as opaque data and ignored.
.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 .
.IR Dial 's
.IR local ,
.IR dir ,
and
.I cfdp
arguments
are not supported and must be zero.
.PP
.I Announce
and
.I listen
are the complements of
.IR 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 netaddr
used in announce may be a local address or an asterisk,
to indicate all local addresses, e.g.
.BR tcp!*!echo .
The
.I listen
routine takes as its first argument the
.I dir
of a previous
.IR 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
.BR ORDWR .
.PP
.I Netmkaddr
makes 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.
.PP
.I Dialparse
parses a network address as described above
into a network name, a Unix domain socket address,
an IPv4 host address, and an IPv4 port number.
.\" .PP
.\" .I Getnetconninfo
.\" returns a structure containing information about a
.\" network connection.  The structure is:
.\" .EX
.\"   typedef struct NetConnInfo NetConnInfo;
.\"   struct NetConnInfo
.\"   {
.\" 	char	*dir;		/* connection directory */
.\" 	char	*root;		/* network root */
.\" 	char	*spec;		/* binding spec */
.\" 	char	*lsys;		/* local system */
.\" 	char	*lserv;		/* local service */
.\" 	char	*rsys;		/* remote system */
.\" 	char	*rserv;		/* remote service */
.\"   };
.\" .EE
.\" .PP
.\" The information is obtained from the connection directory,
.\" .IR conndir .
.\" If
.\" .I conndir
.\" is nil, the directory is obtained by performing
.\" .IR fd2path (3)
.\" on
.\" .IR fd .
.\" .I Getnetconninfo
.\" returns either a completely specified structure, or
.\" nil if either the structure can't be allocated or the
.\" network directory can't be determined.
.\" The structure
.\" is freed using
.\" .IR freenetconninfo .
.\" .PP
.\" .I Setnetmtpt
.\" copies the name of the network mount point into
.\" the buffer
.\" .IR to ,
.\" whose length is
.\" .IR tolen .
.\" It exists to merge two pre-existing conventions for specifying
.\" the mount point.
.\" Commands that take a network mount point as a parameter
.\" (such as
.\" .BR dns ,
.\" .BR cs
.\" (see
.\" .IR ndb (8)),
.\" and
.\" .IR ipconfig (8))
.\" should now call
.\" .IR setnetmtpt .
.\" If
.\" .I from
.\" is
.\" .BR nil ,
.\" the mount point is set to the default,
.\" .BR /net .
.\" If
.\" .I from
.\" points to a string starting with a slash,
.\" the mount point is that path.
.\" Otherwise, the mount point is the string pointed to by
.\" .I from
.\" appended to the string
.\" .BR /net .
.\" The last form is obsolete and is should be avoided.
.\" It exists only to aid in conversion.
.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
Connect to a Unix socket served by
.IR acme (4):
.IP
.EX
int dialacme(void)
{
	return dial("unix!/tmp/ns.ken.:0/acme", 0, 0, 0);
}
.EE
.PP
Announce as
.B kremvax
on TCP/IP 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];

	acfd = announce("tcp!*!7", adir);
	if(acfd < 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;
		}
	}
}
.EE
.SH SOURCE
.B \*9/src/lib9/dial.c
.br
.B \*9/src/lib9/announce.c
.br
.B \*9/src/lib9/_p9dialparse.c
.SH DIAGNOSTICS
.IR Dial ,
.IR announce ,
and
.I listen
return \-1 if they fail.
.SH BUGS
To avoid name conflicts with the underlying system,
.IR dial ,
.IR announce ,
.IR listen ,
.IR netmkaddr ,
and
.I reject
are preprocessor macros defined as
.IR p9dial ,
.IR p9announce ,
and so on;
see
.IR intro (3).