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WebSocket monitor is an extension for Firefox developer tools that can be used to monitor WebSocket connections in Firefox. It allows to inspect all data sent and received.

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Test Page

Prerequisites

• WebSocket Monitor requires Firefox 44 (nightly build)
• The extension isn't signed, so you might need to set xpinstall.signatures.required pref to false.

Features

• Frame Inspection
• Frame Filtering
• Summary Data
• Themes
• Socket.IO Support
• SockJS Support
• JSON Support
• Table and List Perspectives
• Inline Data Preview
• Pause Monitoring

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Start With WebSocket Monitor

When you open Firefox developer Toolbox (press F12) you should see a new Web Sockets panel. Select the panel and open e.g. this simple test page. Initiate web socket connection on the page and see list of frames appearing in the panel.

Frame Inspection

It's possible to inspect all sent and received WS frames. The extension visualizes frame meta data as well as the payload.

• Select a frame in the list of frames
• All details are displayed on the right side

Frame Filtering

The extension allows simple filtering of frames. It's possible to filter the list of frames using a keyword. Only frames that contains the keyword in the payload are displayed.

Summary Data

There is a quick summary displayed at the bottom of the frame list.

• Number of frames in the list
• Total size of transferred payload
• Total time since the first frame

Themes

Both built-in DevTools themes (Dark and Light) are supported. If you have Firebug 3 (aka Firebug.next) installed you can also use Firebug theme.

• Firebug Theme
• Light Theme
• Dark Theme

Socket.IO Support

Socket.IO library has an extra support. Payload of all frames is parsed and visualized as an expandable tree.

• Select a frame generated using Socket.IO
• Check out the Socket.IO side-bar

SockJS Support

SockJS library is also supported. Payload of all frames is parsed and visualized as an expandable tree.

• Select a frame generated using SockJS
• Check out the SockJS side-bar

JSON Support

If the frame payload is formatted as pure JSON the monitor shows a side panel that visualizes it as an expandable tree (similarly to how Socket.IO and SockJS data are displayed).

Table and List Perspectives

There are two ways how to visualize frames. Apart from the tabular view (see screenshots above) there is also a list view that uses well know 'chat' approach (well known from various messengers).

Inline Data Preview

The List perspective offers also an inline data preview. You don't have to always select the frame and go to the side bar, just open the data directly in the frame.

Pause Monitoring

It's possible to pause/unpause monitoring of frames. Just click Pause button that is available on the toolbar within the WebSockets panel.