exposing proxySocket on socket to support sniffing messages coming from proxy target

Created by: thlorenz

Basically I need access to the proxySocket in order to listen to messages coming back.

I realize the implementation is a bit hacky, but it's the only way I could think of ATM. I'm open for other suggestions.

Here is an example use case taken from chromium-remote-debugging-proxy

socket.on('data', function ondata(data) {
    if (socket.proxySocket) {
      socket.proxySocket.on('data', function ondata(data) {
        retHybi.parse(data)
      })
     socket.proxySocket = undefined;
    }
})

If there is an existing way to make this work, please let me know as well.