axigate

AX.25 ↔ APRS-IS bidirectional gateway for networked TNCs. Forwards packets bidirectionally between KISS TNCs and APRS-IS servers.

What it is

A bidirectional gateway that connects KISS TNCs (AX.25) to APRS-IS servers:

• RF to Internet (RX-iGate): Decode packets from TNC and forward to APRS-IS with path annotation
• Internet to RF (TX-iGate): Receive packets from APRS-IS and transmit to RF via TNC (encapsulated format)
• Path annotation: Adds qAR and gateway callsign to packet path for RF→IS packets
• Directional control: Enable or disable each direction independently

Quick Start

# Enable RF to APRS-IS forwarding only (RX-iGate mode)
axigate -h 192.168.0.9 -p 8144 -s aprs.server.com -P 14580 -c MYCALL -r

# Enable both directions (bidirectional gateway)
axigate -h 192.168.0.9 -p 8144 -s aprs.server.com -P 14580 -c MYCALL -r -i

# Unix socket TNC
axigate -x /run/tnc.sock -s aprs.server.com -P 14580 -c MYCALL -r

# Configuration file
axigate -c axigate.conf

Important: By default, no forwarding is enabled. You must use -r (RF→IS) and/or -i (IS→RF) flags to enable packet forwarding.

Build and installation

Prerequisites

• Linux
• GCC or Clang
• CMake

git clone https://github.com/xdab/axigate.git
cd axigate
mkdir build && cd build
cmake .. -DCMAKE_BUILD_TYPE=Release
make
sudo make install

Command Line Arguments

Short	Long	Description
-c FILE	--config=FILE	Configuration file
-h ADDR	--host=ADDR	TNC TCP address
-p PORT	--port=PORT	TNC TCP port (default: 8144)
-x SOCK	--socket=SOCK	TNC Unix socket path
-s SSID	--ssid=SSID	Gateway SSID (default: 0)
-S ADDR	--is-host=ADDR	APRS-IS server address (default: rotate.aprs2.net)
-P PORT	--is-port=PORT	APRS-IS server port (default: 14580)
-f FILTER	--is-filter=FILTER	APRS-IS filter string
-C CALL	--call=CALL	Gateway callsign
-r	--rf-to-is	Enable RF to APRS-IS forwarding
-i	--is-to-rf	Enable APRS-IS to RF forwarding
-v		Verbose logging
-V		Debug logging

Configuration File

Optionally, configuration can be read from a file using -c FILE or --config=FILE.

The file uses simple key=value syntax with # comments.

Example

# axigate.conf
# TNC connection (TCP or Unix socket)
host=192.168.0.9
port=8144
# socket=/tmp/tnc.sock

# Gateway identity (for APRS-IS path annotation)
call=MYCALL
ssid=0

# APRS-IS connection
is-host=aprs.server.com
is-port=14580
is-filter=m/20
is-passcode=12345

# Enable forwarding directions
rf-to-is=true
is-to-rf=false

# Logging: standard, verbose, debug
log-level=verbose

How It Works

RF to Internet (RX-iGate)

1. Receive KISS frames from TNC
2. Decode AX.25 packet
3. Validate packet (check for RFONLY/NOGATE, ignore encapsulated packets)
4. Add qAR and gateway callsign to path
5. Convert to TNC2 format and send to APRS-IS

Internet to RF (TX-iGate)

1. Receive packet from APRS-IS (TNC2 format)
2. Parse AX.25 packet
3. Replace path with TCPIP marker and gateway callsign
4. Encapsulate original packet in } format
5. Send to TNC as KISS frame

Dependencies

• libtnc: included as a git submodule
  • AX.25 packet parsing/construction
  • KISS frame encoding/decoding
  • TCP/Unix socket utilities
• libcomm: included as a git submodule
  • TCP/Unix socket clients
  • Socket polling

Installation

There is a helper Make target make install which handles everything from compilation to asking for SU rights and installing files to the relevant directories.

Systemd service axigate.service will be installed as well. Please review the unit file and adjust for your needs.

License

GNU General Public License v3.0 - see LICENSE

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Development notes: See .clinerules for AI-friendly technical documentation.