Setting Up Fiddler to Capture Traffic

Fiddler is a powerful web debugging proxy tool that allows you to inspect and analyze HTTP and HTTPS traffic between your computer and the internet. It's widely used for debugging web applications, testing APIs, and monitoring network traffic. Here's a step-by-step guide to setting up Fiddler and configuring it to capture traffic, including HTTPS traffic.

Why Use Fiddler?

Fiddler can be used for various purposes, including:

• Debugging Web Applications: Inspect and debug HTTP requests and responses.
• Performance Testing: Analyze the performance of web applications by monitoring network traffic.
• Security Testing: Identify security vulnerabilities by inspecting HTTPS traffic.
• API Testing: Test and debug API calls by capturing and analyzing the traffic.

Steps to Set Up Fiddler

1. Download and Install Fiddler:

   • Visit the Fiddler website and download the appropriate version for your operating system.
   • Follow the installation instructions to install Fiddler on your computer.

2. Start Fiddler:

   • Launch Fiddler after installation.

3. Enable Traffic Capturing:

   • Fiddler starts capturing traffic by default. You can toggle this by clicking on File > Capture Traffic.

4. Capture HTTPS Traffic:

   • To capture HTTPS traffic, you need to configure Fiddler to decrypt HTTPS traffic:
     • Go to Tools > Options > HTTPS.
     • Check Capture HTTPS CONNECTs and Decrypt HTTPS traffic.
     • Fiddler will prompt you to install a root certificate. Accept and install it to your trusted root store.

5. Configure .NET Applications:

   • To ensure .NET applications route their traffic through Fiddler, you need to modify the machine.config file:
     • Open the file located at C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Config\machine.config.
     • Add the following entry just below the closing tag of system.web at the bottom of the file:

       </system.web> <!-- Is already in the file -->
       
       <system.net>
           <defaultProxy enabled="true" useDefaultCredentials="true">
               <proxy autoDetect="false" bypassonlocal="false" proxyaddress="http://127.0.0.1:8888" usesystemdefault="false" />
           </defaultProxy>
       </system.net>
       
       </configuration>
       

     • Save the changes.

6. Restart IIS and Ometa Services:

   • Perform an IIS reset by running iisreset in the command prompt.
   • Restart all Ometa services to apply the changes.

7. Optionally, Configure Your Browser or Application:

   • Ensure your browser or application is set to use Fiddler as a proxy. Fiddler usually sets this up automatically, but you can manually configure it if needed:
     • For browsers, go to the proxy settings and set the HTTP and HTTPS proxy to 127.0.0.1 and port 8888.

8. Filter and Inspect Traffic:

   • Use the Filters tab in Fiddler to include or exclude specific traffic.
   • Click on individual sessions in the left pane to inspect details like headers, body, cookies, etc.

9. Save and Export Sessions:

   • Save captured sessions for later analysis by going to File > Save > All Sessions.

By following these steps, you can effectively set up Fiddler to capture and analyze both HTTP and HTTPS traffic, making it a valuable tool for web development and debugging.