ref: 948870cffe2572efb68ef0b3873b36238fb53263
dir: /man/2/sys-dial/
.TH SYS-DIAL 2
.SH NAME
announce, dial, listen \- make network connections
.SH SYNOPSIS
.EX
include "sys.m";
sys := load Sys Sys->PATH;
Connection: adt
{
dfd: ref FD; # data file
cfd: ref FD; # control file
dir: string; # pathname of line directory
};
announce: fn(addr: string): (int, Connection);
dial: fn(addr, local: string): (int, Connection);
listen: fn(c: Connection): (int, Connection);
.EE
.SH DESCRIPTION
These routines in the
.B Sys
module are still used by some existing code.
They are deprecated, and new applications should use the
.B Dial
module described in
.IR dial (2).
.PP
These routines establish network connections.
Their description uses the following definitions:
.TF network
.PD
.TP
.I addr
is a network address in one of the following forms:
.br
.IP
.IB network ! netaddr ! service\f1
.br
.IB network ! netaddr\f1
.br
.IR netaddr
.TP
.I network
Any directory listed in
.B /net
(eg,
.BR tcp ),
or the special token,
.BR net .
The name
.B net
acts as a free variable that stands for any network in common
between the source and
.IR netaddr .
A network name can be preceded by the full path name of a directory
of networks, using the form
.I /dir/network
(eg,
.BR /net.alt/tcp ).
.TP
.I netaddr
A host name, a domain name, a network address,
or a meta-name of the form
.BI $ attribute\f1,
which
is replaced by
.I value
from the corresponding attribute-value pair
in the connection server data base (see
.IR db (6)).
.PP
The functions
.B dial
and
.B announce
translate a given
.I addr
to an actual network address using
the connection server
.IR cs (8).
If a logical name
.I addr
corresponds to several network addresses,
for instance if a destination machine has several interfaces,
.I cs
will return them all.
In particular, if
.I addr
is
.BR net ,
.I cs
will return addresses on
all networks that are common to source and destination.
The translation procedure accesses
.I cs
using its interface file
.BR cs ,
which is sought as follows:
first, in an explicit directory
.BI / dir
if one was given in
.IR network ;
second, in the standard directory
.BR /net ;
and finally in the directory
.BR /net.alt
.RB ( dial
only).
If the connection server cannot be found,
the
.I addr
is used as-is.
.PP
If a connection attempt is successful, the
.B dir
member of the resulting
.B Connection
will be
the path name of a
.I line directory
that has files for accessing the connection.
One line directory exists for each possible connection.
The
.B data
file in the line directory is opened to
make a connection, and read and written to communicate with the destination.
The
.B ctl
file in the line directory can be used to send commands to the line.
See
.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.
The
.B remote
file in the line directory contains the address called; the file
.B local
contains the local address assigned.
.PP
The
.B dial
routine
makes a call to destination
.I addr
on a multiplexed network.
If the connection server returns several addresses,
.B dial
tries each in turn, until a connection is made
or no addresses remain to be tried.
It returns a
.B Connection
containing a file descriptor
.B dfd
open for reading and writing the
.B data
file in the line directory,
and a file descriptor
.B cfd
open for reading and writing the
.B ctl
file.
If
.IR local
is non-empty, and
the network allows the local address to be set,
as is the case with UDP and TCP port numbers,
the local address will be set to
.IR local .
.PP
.B Announce
and
.B listen
are the complements of
.BR dial .
.B Announce
establishes a network name to which incoming calls can be made.
In
.IR addr ,
.I netaddr
gives the name or address of one of the local host's interfaces on which to listen for
calls to the given
.IR service ;
it can be
.B *
to listen for calls on any interface on
.IR network .
.B Announce
returns a
.B Connection
structure in which only the
.B cfd
descriptor is open, on the control file representing the announcement.
.B Listen
takes as its only argument the
.B Connection
structure of a successful call to
.BR announce .
When a call is received,
.B listen
returns an open
.B Connection
structure as if from
.BR dial ,
except that only the
.B cfd
descriptor is open,
.B dfd
is nil,
and the caller must open the data file for itself.
.SH EXAMPLES
.PP
Make a call and return an open file descriptor to
use for communications:
.IP
.EX
callkremvax(): (int, Connection)
{
return sys->dial("tcp!kremvax!80", nil);
}
.EE
.PP
Call the local certificate signer:
.IP
.EX
dialsigner(service: string): (int, Connection)
{
return sys->dial("net!$SIGNER!inflogin", nil);
}
.EE
.SH SOURCE
.B /emu/port/inferno.c
.br
.B /emu/port/dial.c
.br
.B /os/port/inferno.c
.br
.B /os/port/dial.c
.SH DIAGNOSTICS
The integer valued functions return 0 on success and -1 on error;
the system error string is set.
The integer component of the tuple returned by the other functions
follows the same convention.
.SH BUGS
Note that
.B listen
does not open the
.B data
file.