Fiddler not showing websocket protocol using ws prefix

Simeon,

How is this related to what I'm asking? What kind of network setup are you asking for? What kind of network configuration would keep Fiddler from seeing the ws prefixed messages? Can you see ws prefixed communications in your version or configuration of Fiddler? I'm just not sure it's supported. Can you let me know if it's supported?

Hi Simeon,

Via Fiddler 5 i was able to view websockets request but can you please provide solution how to compose a same websocket request or export same Websocket request to a curl request.

Hi Divik,

You can compose a WebSocket request the same way you can compose any other HTTP request with the Composer. You can drag and drop the WebSocket request session, which Fiddler captured, from the Session list to the Composer tab.

You can also export the session to a cURL Script which is basicaly a bat file with the curl command which produces the same request.

Please, note that both the compose and the export handle only the upgrade to websocket request message. You cannot compose or export any messages sent on the WebSocket connection. Both Fiddler and curl are not designed for this. However, with Fiddler once you capture a WebSocket connection, you can modify the messages with the FiddlerScript by adding a OnWebSocketMessage function to it.

// ...

class Handlers
{
    static function OnWebSocketMessage(oMsg: WebSocketMessage) {
        // Conditionally modify message content
        var sPayload = oMsg.PayloadAsString();
        if (sPayload.Contains("time")) {
            oMsg.SetPayload(sPayload + "... bazinga!");
        }
        // FiddlerApplication.Log.LogString(oMsg.ToString());
    }

// ...

Regards,
Simeon
Progress Telerik

Hi Simeon,

Thanks, One more query I'm unable to intercept a Particular request via android emulator using Fiddler same If i try to intercept via SMSniff I'm able to. Please Check Attached snapshot or request.

I don't see the websocket tab even though I have web socket traffic captured. I've attached a screenshot

Here are the details of the version of Fiddler that I'm using:

v5.0.20202.18177 for .NET 4.6.1
Built: 14 April 2020

64-bit AMD64, VM: 196.0mb, WS: 263

Hi Shiraz,

When a WebSocket session is captured the icon next to the session number will be different than a HTTP/S session. To quickly test capturing Web Sockets use https://www.websocket.org/echo.html. For additional reference, see the attached video walkthrough as well. 

Please give this a try and let us know if you experience any additional issues. Thank you.

Regards,

Eric R | Senior Technical Support Engineer
Progress Telerik

Hi Colin,

Seems capturing  WebSocket works on your fiddler. Could you please share how you configured and got it work? :)

By searching the solutions, find someone says add several lines code in Fiddler script, a WebSocket tab will appear next to Timeline tab. But I don't find new tab shows after adding codes. No WebSocket session is captured. I think the code doesn't work. 

The code added: 

static function OnWebSocketMessage(oMsg: WebSocketMessage) {
// Log Message to the LOG tab
FiddlerApplication.Log.LogString(oMsg.ToString());
}

That may be the reason why I don't see the "Parse WebSocket Messages" options under the "Performance" tab.

Hi Carina,

I've just tested capturing WebSocket traffic in Fiddler on a new installation and it's working fine. Here's what I did:

- Make sure "Parse WebSocket Messages" is checked in Fiddler Options -> Performance.

- With capture enabled, navigate to http://websocket.org/echo.html (to prevent problems due to https, make sure you've really loaded the page over http - you should see a security warning somewhere, in chrome in the address bar. If you load the page over https you can change manually change the web socket location to use ws instead of wss, but the browser will probably refuse to connect over ws - with Chrome in the console you will see a warning about trying to initiate an insecure connection from a page loaded over https.)

- Click on the connect button for default location ws://echo.websocket.org. The request should appear in Fiddler's sessions list, but note that at this point double clicking the ws session did not open the inspector tab for me.)

- Click on the Send button to send the default message "Rock it with HTML5 WebSocket"

- Go to Fiddler and double click on the ws session (there will still only be one session open.) At this point the WebSocket session tab opens showing details of all the messages sent over the socket.

Tested with Fiddler v5.0.20182.28034 on Windows 10 using Chrome Canary. Fiddler book has some pretty good information on capturing Web Sockets and is highly recommended - make sure you have at least v 2.03 (the Performance Tab for example is not described in v4.01 of the book.) 

Hi Colin,

Thanks for your reply and the detailed steps, and sorry for the late response. I tried the steps in your post, indeed Websocket for web can be captured, and I captured Websocket of my company's production, also web end. BTW, is there any chance you happen to know how to capture WS of mobile APP? Though my developer colleague has developed a tool to capture WS from the APP, I still want to find if there is a way to do that via fiddler. :D

Thanks,

Carina

Hi Carina,

Good to hear you got the WebSocket capture working.

In principal capturing connections from an app is fairly simple, although it will depend on having a common wi-fi connection for your mobile device and the PC running fiddler. Steps to do this on Android are (iOS should be similar, but I haven't tried it):

1. In Fiddler options, tab Connections, make sure "Allow remote computers to connect" is checked. You may need to restart Fiddler. Note the port being used by Fiddler - default is 8888. You can disable capturing in Fiddler - the mobile device will send its requests directly to Fiddler.
2. Find the IP address of Fiddler. You can get this by clicking the "Online" button in the tool bar, or typing "about:network" in the QuickExec box. Note the IP address being used by the wi-fi network.
3. In the mobile device, go to Settings -> Wi-fi, select the current wi-fi connection, and choose the option to modify connection. Enable Advanced Options, select Manual proxy, and fill in the IP address of Fiddler as host, and the port being used by fiddler. Save changes and you're set.
4. Go to Chrome and load any page. You should see the requests appearing in Fiddler. 

That's it, now all network requests from the mobile device should go through fiddler. Remember to disable the proxy in you wi-fi settings when you finish testing!

Colin

Hi Colin,

Thanks for your quick reply. You are so helpful ;)

Yes I can capture requests from browser/application on mobile, but I don't find the way to capture Websocket from my company's software, can capture HTTP/S, but no Websocket in session list. If you know how to capture Websocket of software, that would be great.

OK, I've just tried with the websocket.org echo page:
http://websocket.org/echo.html

and it works as with the browser - I can see the ws session in the session list, and on sending a message to the socket the WebSocket tab appears in the inspector.

Can you see WebSocket sessions on connecting to http://websocket.org/echo? Does you application use secure wss protocol? (I haven't been able to trace wss connections from the mobile device, probably due to a problem with certificates.)

Colin

Sorry, me again!

It can be confusing to users that the WebSocket tab is only shown after the first successful connection, and it remains once it is shown. Also the protocol is shown as HTTP (or HTTPS) rather than WS (or WSS)