Firefox 71 will include a built-in WebSocket Inspector, a tool to inspect WebSocket connections. The tool is already available in Firefox Developer Edition 70, an experimental version of the browser.
Found in the Network UI panel in the Developer Edition network panel, the WebSocket Inspector lets users see actual data transferred in WebSocket frames. The WebSocket Inspector leverages the Socket.IO event-based communication engine and SockJS WebSocket emulation client.
Payloads based on these protocols or plain JSON can be parsed and displayed in an expandable tree for inspection. Raw data sent over the wire can be seen as well. A pause/resume button in the Network panel allows you to stop intercepting WebSocket traffic, so you can capture only the frames of interest. Plans call for expanding the tool to support the SignalR library as well. Other goals for the tool include adding support for the following:
- A binary payload viewer.
- Exporting of WebSocket frames.
- Indication of closed connections.
The WebSocket API is used to forge persistent connections between web clients and servers. It is primarily used in applications needing real-time communications.