Listen to chrome websocket debugging interface

Basic workflow

0. Choose the debugging port: i.e. 9222

1. Open your browser with --remote-debugging-port=9222

2. Execute query to http://localhost:9222/json

3. The resulting json is something like this:

   [ {
   "description": "",
   "devtoolsFrontendUrl": "/devtools/inspector.html?ws=localhost:9222/devtools/page/926A781407E057C7AE6A2C6F1E61B371",
   "id": "926A781407E057C7AE6A2C6F1E61B371",
   "title": "Document",
   "type": "page",
   "url": "https://kth.se",
   "webSocketDebuggerUrl": "ws://localhost:9222/devtools/page/926A781407E057C7AE6A2C6F1E61B371"
   } ]

   Every tab in the browser session will be represented in this json object as an array entry. The properties of each entry are: page description, id, title of the page, url of the page and the websocket address to access the debugging interface.

4. Then, open a websocket channel targeting the tab webSocketDebuggerUrl

5. Start to talking to chrome debugging interface like Runtime.enable method call https://chromedevtools.github.io/devtools-protocol/v8/Runtime at open channel event.

   • Runtime channel

   // NodeJS example
   
       ws.send(
           JSON.stringify({{id: 1, method: 'Runtime.enable'}}))

   • Network profiler

   // NodeJS example
   
   ws.send(
       JSON.stringify({{id: 1, method: 'Network.enable'}}))

6. Listen for incoming messages:

// NodeJS example
ws.on('message', function incoming(data) {
    console.log(data);
});

How to execute remote methods ?

Following the DevTools documentation, basically to run it, you need to send a WS message as follows:

{
    "id": "RequestUniqueID",
    "method": "MethodName",
    "params": {
        "key": "value" // For each value described as parameter in documentation
    }
}

The call result is showed in the Runtime listener with the unique sent Id as identifier

{
    "id":"RequestUniqueID",
    "result":
        {
            "result":
            {
                "type":"undefined"
            }
        }
}

Example: Execute JavaScript code in specific page

// NodeJS example

ws.send({
    "id": 4,
    "method": "Runtime.enable"
})

ws.send({
    "id": 2,
    "method": "Runtime.evaluate",
    "params": {
        "expression": "1 + 2"
    }
})

Result

{
    "id":2,
    "result":
    {
        "result":
        {
            "type":"number",
            "value":2,
            "description":"2"
        }
    }
}

Examples

• Create your own integration test tool from scratch Link
• Processing network events Link
• Capture screen images Link