Tracing HTTP Connections
By: Thomas Bayer
Date: 07/20/2009
This document describes how HTTP messages can be captured and analyzed using the Membrane Monitor tool. The primary use case for Membrane Monitor is analyzing SOAP over HTTP traffic. However the tool can also monitor regular HTTP traffic.
Figure 1:
The following paragraphs describe how requests from a Web browser can be send to the monitor, how to inspect the messages and how the messages are routed to its destination. In this example we will trace the traffic to the homepage of predic8. But you can use any Web site, of course.
Download and Startup
After downloading we start the monitor by clicking on run.bat in the expanded archive.
Adding a Routing Rule
Membrane Monitor works as a forwarding HTTP proxy. Based on some simple routing rules HTTP messages are forwarded to its destination. We need a rule that receives requests on port 7000, for instance, and forwards the request to its destination, the host predic8.com.
Click on the Rule menu and choose Add Rule. Fill out the dialog as shown in figure 2.
Figure 2:
Click Add Rule.
Tracing HTTP Traffic
Now we can start tracing HTTP traffic. Open the following URL in Firefox, Microsoft IE or Google Chrome:
http://localhost:7000
Of course you can follow the link above. After requesting the URL you should see our homepage.
Figure 3:
Let's have a look at the monitor and see what was captured. Figure 4 shows a screenshot of the monitor. As you can see, four messages have been captured. An HTTP GET request to the resource / . The response of this request is the HTML code of the Webpage. Inside this page there are three images and a referenced stylesheet.
Figure 4:
Now you can:
- Modify and resend messages
- Change HTTP headers
- Look at the raw messages
I hope you enjoy using the monitor.