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SSL websocket connection on not standard port send to port 443

Tim | Last updated: Feb 23, 2018 08:29AM UTC

I'm trying to intercept secure websocket traffic of an application with burp. I've set up an invisible proxy listener on port 8081 (the port of the websocket server). The websocket upgrade request is captured correctly by burp, but for some strange reason burp sends the request to port 443. Because there is a normal webserver running on this port, the webserver returns status 200 and my application tells me the connection was dropped.

PortSwigger Agent | Last updated: Feb 26, 2018 10:17AM UTC

Hi Tim, Thanks for your message, and apologies for the delay in responding. Is there a reason you used an invisible listener? We normally recommend using a regular proxy. I just tried WebSockets with an invisible proxy and it worked correctly for me. Please check the "Redirect to port" setting in Proxy > Options > Proxy Listeners > Edit > Request handling. This should match the port of the websocket server. Please let us know if you need any further assistance.

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