LinBPQ Applications Interface

Introduction

LinBPQ has a facility to make a tcp connection from the node to an application running on the same machine. This was originally intended to connect to a shell to enable basic configuration editing, but has been generalised to allow connects to other tcp ports, thus allowing you to write your own applications to be used with LinBPQ.

This document describes one way to do this, and includes a sample program. There are other ways, but this works, and is easy to set up. The idea comes from this website.

Note that although this was added for LinBPQ, it ia also available on the Windows version.

LinBPQ Configuration

Allocate a TCP port for each application. You can use any that aren't used by other programs. Add a CMDPORT line to the Telnet Server config listing the port(s)

CMDPORT 23 63000       ;This allows connects to the telnet server and your app

Add  APPLICATION Line for each. These assume your Telnet Port is port 2.

APPLICATION 1,LINUX,C 2 HOST 0 S

APPLICATION 2,DEMO,C 2 HOST 1 S

The number before the S indexes the port numbers in CMDPORT. The S is optional - it means that the user will be returned to the node when he/she closes the application instead of being disconnected.

Normally the connecting user's callsign will be sent to the application. You can add the parameter NOCALL to overrive this.

If your users need to remain connected to the application for long periods without sending any input you can add K to enable Keepalive messages to be sent to the node.

If S is specified it must be after any optional parameters, eg C 2 HOST 1 NOCALL K S.

You can add the usual Callsign, Alias and Quality params after the application definition if you want your application to be accessible from other nodes on the network.

Linux Configuration

Add lines to /etc/services and /etc/inetd.conf for each of your applications

/etc/services

# Local services
bpqdemo        63000/tcp   # BPQ Demo App

/etc/inetd.conf

bpqdemo    stream    tcp    nowait    pi    /home/pi/linbpq/testapp.pl

Change pi to whatever user you run LinBPQ as.

Restart inetd - sudo killall -1 inetd

Sample Program

This simply accepts input and echos it back.The Node sends the call of the user when the ocnnection is made. This is written in perl, as it was the first example I found. Any language could be used. Input is on STDIN, output on STDOUT.

#!/usr/bin/perl -w -T

# sinet.pl A simple inetd socket server.

use strict;

my $old_fh = select(STDOUT);
$| = 1;
select($old_fh);
my $line = ;
print "Hello " . $line . "Welcome to my LinBPQ Demo App. type exit to close\n";
while( my $line =  )
{
    $line =~ s/\r?\n$//;
    if ($line =~ /exit/) 
    {
        die "shutting down\n";
    }

    # do your processing here!

    print "  $line\n";
}

This can be downloaded from here. Save in your linbpq directory and set as executable.