go-m17-listen

go-m17-listen is a Go program that connects to an M17 relay or reflector as a listen-only client. It decodes M17 voice packets using the Codec 2 vocoder and plays the audio through the speakers.

Features

• Connects to an M17 relay or reflector as a listen-only client.
• Decodes M17 voice packets using Codec 2.
• Plays decoded audio through the speakers.
• Handles optional module letters for mrefd reflectors.
• Gracefully shuts down and waits for a DISC packet from the relay.

Installation

1. Install Codec 2 Library

   Follow the instructions on the Codec 2 repository to install the Codec 2 library on your system.

2. Install Go

   Make sure you have Go installed on your system. You can download and install Go from the official website.

   Recommended version: 1.20 or later.

3. Install any required dependencies

   • GLFW and OpenGL Libraries:

     These are required for the fyne GUI library which depends on glfw for window management. Install the necessary development packages:

     sudo apt-get install libgl1-mesa-dev xorg-dev

   • X11 Development Libraries:

     These are required for glfw and other graphical dependencies. Install the necessary development packages:

     sudo apt-get install libx11-dev libxcursor-dev libxrandr-dev libxinerama-dev libxi-dev libxxf86vm-dev

   • ALSA (Advanced Linux Sound Architecture):

     Required for audio playback using the oto library. Install the necessary development package:

     sudo apt-get install libasound2-dev

4. Clone the Repository

   git clone https://github.com/kc1awv/go-m17-listen.git
   cd go-m17-listen

5. Install Go Dependencies

   go mod tidy

6. Run or build the Program

   • Build and run the program

   go build
   ./go-m17-listen [--tui | --gui] <relay_address>:<port> [module]

   • Run the program (without building)

   go run . [--tui | --gui] <relay_address>:<port> [module]

Usage

• --tui: Run program with TUI interface
• --gui: Run program with GUI interface
• <relay_address>: The address of the M17 relay or reflector to connect to.
• <port>: The port the relay or reflector is listening on.
• <module_letter>: The optional module letter for mrefd reflectors.

Example

• relay: ./go-m17-listen --gui 127.0.0.1:17000
• mrefd: ./go-m17-listen --tui 127.0.0.1:17000 A

TUI Interface

GUI Interface

Configuration

The program generates a random 9-character callsign starting with "LSTN" followed by 5 random characters (letters A through Z and digits 0 through 9).

Handling Packets

The program sends the following packets:

• LSTN: Send a listen-only connection request to the relay or reflector.
• PONG: Sends a PONG to the relay or reflector in response to a PING keepalive.
• DISC: Disconnect from the relay or reflector.

The program handles the following packet types:

• PING: Responds with a PONG packet.
• ACKN: Logs that the connection was accepted.
• NACK: Logs that the connection was not accepted and gracefully shuts down.
• DISC: Logs that a DISC packet was received and signals the program to shut down.
• M17: Decodes and plays the voice stream using Codec 2.

Graceful Shutdown

When the program receives a termination signal (SIGINT or SIGTERM), it sends a DISC packet to the relay and waits for a DISC packet from the relay before closing the connection. If no DISC packet is received within 5 seconds, the program times out and closes the connection.

License

This project is licensed under the GNU General Public License v3.0. See the LICENSE file for more details.

Acknowledgements

Codec 2 - Open source low bit rate speech codec.

Oto - A low-level library to play sound on multiple platforms.

termbox-go - Pure Go termbox implementation.

Fyne.io - An easy to learn toolkit for creating graphical apps for desktop, mobile and web.

Contributing

Contributions are welcome! Please open an issue or submit a pull request on GitHub.