foxglove_json_server

A lightweight UDP-to-Foxglove bridge that live-streams JSON telemetry and records it to MCAP

Features

• Listens for JSON telemetry on UDP
• Streams messages live to Foxglove Studio
• Writes all data to an .mcap file in a crash-safe manner

Repository Structure

foxglove_json_server.py   # Main server
foxglove_json_demo.py     # Test data sender
foxglove_json_layout.json # Example Lichtblick dashboard layout

Quick Start

Install (the opensouce foxglove-studio alternative)

Install dependencies pip install foxglove-websocket mcap

Start the server python foxglove_json_server.py

Then open Lichtblick -> Add connection -> WebSocket -> ws://localhost:8765.

Optional: Load foxglove_json_layout.json in Lichtblick for instant dashboard UI.

In another shell (sends demo JSON over UDP) python foxglove_json_demo.py

Data Flow Architecture

[Your telemetry source]
        | (UDP JSON)
        V
foxglove_json_server.py --> Foxglove Studio (live telemetry)
        |
        --> .mcap file recording

• Receives JSON on UDP 0.0.0.0:9999
• Broadcasts over Foxglove WebSocket 0.0.0.0:8765
• Writes every packet to MCAP file for offline replay

Example JSON Packet

{
  "voltage": 12.5,
  "temperature": 33.7,
  "status": "OK"
}

• Receives datagrams on UDP 0.0.0.0:9999
• Broadcasts JSON data live via Foxglove WebSocket
• Records messages into timestamped .mcap file

Advanced Usage

Change Ports / Channel Name

Modify udp_listen, foxglove_listen, channel_name in the script directly.

Replaying MCAP Later

Open lichtblick, click File -> Open Data -> Select your .mcap recording

Behaves exactly like a live stream.

Integrating with Real Hardware

Just send raw JSON bytes over UDP to 0.0.0.0:9999:

sock.sendto(b'{"rpm":1200,"temp":42.1}', ("localhost", 9999))

License

MIT