When you connect to a BPQ32 Node, you may be offered custom applications as well as the standard commands:

ABNGDN:G6FJI} BBS CHAT HARS CONNECT BYE INFO NODES PORTS ROUTES USERS MHEARD

Here the first three commands are applications defined in the nodes configuration file, bpq32.cfg:

APPLICATION 1,BBS,,G6FJI-2,ABIBBS,254
APPLICATION 2,CHAT,,G6FJI-1,ABICHT,254
APPLICATION 3,HARS,C 1 HARS S

Applications 1 and 2, BBS and CHAT are standard features in BPQ32; Application 3 is simply a user shortcut: typing HARS is the same as typing C 1 HARS S.

BPQ32 also has a facility to make a TCP connection to a port on the same machine, which allows you to create custom applications within your node. This page describes setting up an application on a Linux system using systemd - I have not seen any documentation to make this work on Windows.

This example assumes you have a 'standard' BPQ32 installation running on Linux, with Port 1 using RF and Port 2 using Telnet.

First we must add a CMDPORT line to the Telnet Port. The syntax is CMDPORT <TCP port 0> <TCP port 1> … <TCP port n>, eg:

  CMDPORT 63001 63002

Then we add a Node APPLICATION which calls that port. The options used here are:

• Application number
• Application name
• Command to execute
• User to connect as

  APPLICATION 5,HELLO-WORLD,C 2 HOST 0 S,G6FJI

The command syntax is C(onnect) <port> HOST <zero-based command port number> S; the S at the end means return to the current session rather than disconnect completely.

Our 'Hello World' application is simply a bash script called as a systemd service. Using your editor of choice, create a file 'hello-world.sh' containing this script:

#!/bin/bash
echo "Hello world"

Make the script executable and check you can run it:

martinr@UbuMini:~$ chmod +x hello-world.sh
martinr@UbuMini:~$ ./hello-world.sh
Hello world

Now we need to set up the systemd service to call the script. This is in two parts - the socket and the service. First create the socket part with sudo nano /lib/systemd/system/hw.socket

[Unit]
Description=Hello World

[Socket]
ListenStream=63001
Accept=yes

[Install]
WantedBy=sockets.target

The bit that matters here is the port number in the ListenStream must match the CMDPORT you created in the BPQ configuration.

Then we need the matching service file: sudo nano /lib/systemd/system/hw@.service - note the @ in the name.

[Unit]
Description=Hello World Server

[Service]
ExecStart=/home/martinr/hello-world.sh
StandardInput=socket

Here the important parts are the script to run and the line telling it to take standard input from the socket - there won't be a keyboard connected to the service.

Reload the systemd configuration and start the service, then test it using netcat:

martinr@UbuMini:~$ sudo systemctl daemon-reload
martinr@UbuMini:~$ sudo systemctl start hw.socket
martinr@UbuMini:~$ nc localhost 63001
Hello world

To have the new service run on start up, run this command:

martinr@UbuMini:~$ sudo systemctl enable hw.socket

Finally restart your node and test:

ABNGDN:G6FJI} BBS CHAT HARS HELLO-WORLD CONNECT BYE INFO NODES PORTS ROUTES USERS MHEARD
HELLO-WORLD
Connected to HELLO-WORLD 
Hello world
Returned to Node ABNGDN:G6FJI

• packet:AuthServer OTP authentication server that has a configurable menu that can call a URL (useful for remote controlling/monitoring of a node)
• Temperature graph
• packet:ADSB_latest_script

I found these links useful in getting this to work:

The official documentation uses inetd and doesn't really explain the significance of the port list in the CMDPORT line:
https://www.cantab.net/users/john.wiseman/Documents/LinBPQ%20Applications%20Interface.html

This presentation is quite helpful once you work out the typos and which bits are meant to be there:
https://www.prinmath.com/ham/talks/BPQ.pdf

These pages were useful for understanding the systemd services and testing them
https://www.linux.com/training-tutorials/writing-systemd-services-fun-and-profit/
https://mgdm.net/weblog/systemd-socket-activation/

Here is a completely separate write-up
https://labby.co.uk/linbpq-bpq32-linux-add-custom-application/

Another approach: https://github.com/bradbrownjr/bpq-apps