ref: a920c765f2b4130590fb5971a50690b21664957a
dir: /man/2/dial/
.TH DIAL 2
.SH NAME
Dial: accept, announce, dial, listen, netinfo, netmkaddr, reject \- make network connections
.SH SYNOPSIS
.EX
include "dial.m";
dial := load Dial Dial->PATH;
Connection: adt
{
dfd: ref FD; # data file
cfd: ref FD; # control file
dir: string; # pathname of line directory
};
announce: fn(addr: string): ref Connection;
dial: fn(addr, local: string): ref Connection;
listen: fn(c: ref Connection): ref Connection;
accept: fn(c: ref Connection): ref Sys->FD;
reject: fn(c: ref Connection, why: string);
netmkaddr: fn(addr, defnet, defsvc: string): string;
Conninfo: adt
{
dir: string; # connection directory
root: string; # network mount point
spec: string; # its binding spec
lsys: string; # local host address
lserv: string; # local service
rsys: string; # remote host address
rserv: string; # remote service
laddr: string; # local address in dial form
raddr: string; # remote address in dial form
};
netinfo: fn(c: ref Connection): ref Conninfo;
.EE
.SH DESCRIPTION
.B Dial
establishes network connections.
The description below 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 special name
.B net
stands for any network that connects
the current host 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;
.B dial
or
.B announce
will try each in turn until one works.
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 both
.B data
and
.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 function
.B dial
calls destination
.I addr
on a multiplexed network.
If the connection server returns several possible locations for
.IR addr ,
.B dial
tries each in turn, until a connection is made,
or no address remains to be tried.
.B Dial
returns a reference to a
.B Connection
value containing a string
.B dir
that names the conversation directory for the connection,
a file descriptor
.B dfd
open for reading and writing the
.B data
file in that directory, and
a file descriptor
.B cfd
open for reading and writing the directory's
.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 reference to a
.B Connection
value in which only the
.B cfd
descriptor is open, on the control file representing the announcement.
.B Listen
takes as its only argument a reference to the
.B Connection
returned by a successful call to
.BR announce .
When a call is received,
.B listen
returns a reference to a new
.B Connection
value that refers to the conversation directory for the incoming call;
only the
.B cfd
descriptor is open.
That call can be accepted or rejected.
Use
.B accept
to obtain a file descriptor for the data file for the conversation.
Use
.B reject
to reject the incoming call; some networks will also tell the caller the reason
.IR why .
.PP
.B Netmkaddr
makes
.I addr
into a full network address,
suitable for
.B dial
or
.BR announce .
It adds the default network
.I defnet
(usually "\f5net\fP")
and a default service
.I defsvc
to the given
.I addr
as required, including
.RB ` ! '
separators,
and returns the result.
.PP
Given a
.BR Connection ,
.B netinfo
returns a reference to a
.B Conninfo
value that gives details about the connection and its network.
.SH EXAMPLES
.PP
Make a call and return an open file descriptor to
use for communications:
.IP
.EX
callkremvax(): ref Sys->FD
{
c := dial->dial("tcp!kremvax!80", nil);
if(c == nil)
return nil;
return c.dfd;
}
.EE
.PP
Call the local certificate signer:
.IP
.EX
dialsigner(service: string): ref Sys->FD
{
c := dial->dial("net!$SIGNER!inflogin", nil);
if(c == nil)
return nil;
return c.dfd;
}
.EE
.PP
Listen for incoming calls.
.IP
.EX
listener()
{
ac := dial->announce("tcp!*!9995");
if(ac == nil){
sys->print("can't announce: %r\en");
exit;
}
for(;;){
lc := dial->listen(ac);
if(lc == nil){
sys->print("listen: %r\en");
exit;
}
sys->print("incoming: %s\en", hd ctext(lc));
spawn client(lc);
}
}
client(c: ref Connection)
{
dfd := dial->accept(c);
if(dfd == nil){
sys->print("%s: can't accept: %r\en", c.dir);
exit;
}
buf := array[Sys->ATOMICIO] of byte;
while((n := sys->read(dfd, buf, len buf)) > 0)
sys->write(dfd, buf, n);
}
.EE
.SH SOURCE
.B /appl/lib/dial.b
.SH DIAGNOSTICS
The integer valued functions return 0 on success and -1 on error;
functions returning a reference return nil on error.
In those cases the system error string is set.