How to log HTTP traffic in Fiddler for a Native App communicating with a VirtualBox server?

Question

I have a Windows 7 host machine running Fiddler and a Ubuntu VirtualBox guest. On the host I'm running a client app (native, not .NET or Java) that allows me to set the server name and port but there are no proxy setting options. It's connecting to a REST server running in the Ubuntu guest.

It works fine making calls into and out of the guest but I haven't been able to get Fiddler to log the traffic. I tried setting up a Rule (though I'm not sure I did it correctly) and tried instructions for using Fiddler as a reverse proxy and setting up an outgoing port on the Ubuntu machine without success.

If I point the client to 127.0.0.1 and port 8888 I can see the first request but that's about it (and the client obviously doesn't work configured like this).

Does someone know what steps I can take to get Fiddler logging the traffic?

Answer 1

I finally got this working, although I'm not at all sure this is the "best" solution, it is capturing all the traffic as I needed.

I did the following:

1. In Fiddler, I went to Rules->Custom Rules.. .
2. I added the following to the top of the OnBeforeRequest() function:

Code:

if (oSession.host=="127.0.0.1:8888") {
    oSession.bypassGateway = true;
    oSession.host="192.168.56.1:9876"; // This is the IP/Port of my guest OS / service
}

3. I set my client application to IP 127.0.0.1 and port 8888.
4. I added a Filter to restrict the traffic to only that coming from my client application.

This is dirty but it does the trick.