SoapProxyApp: Lightweight HTTP & SOAP API Debugger

SoapProxyApp is an open-source HTTP/HTTPS traffic monitor and API mocking tool for Windows. Designed specifically for .NET developers working with WCF, SOAP, and REST web services, it serves as a fast, lightweight, and portable alternative to Fiddler, Charles Proxy, or Postman.

Key Features

• API Auto-Responder & Mocking: Intercept outgoing API requests and return fake payloads to test edge-cases, simulate offline development, or inject 500 Server Errors without touching the real backend.
• Intercept HTTP/HTTPS request and response packets (Explicit or Global System Proxy)
• Replay / Resend Requests to the server with modified headers and body, on the fly!
• View raw Headers, Raw Body, Formatted XML, Formatted JSON, HTML, and Images
• Automatic conversion from SOAP XML to formatted JSON for easier reading
• Collapsible syntax-highlighted code editors for XML and JSON (AvalonEdit)
• Compare two requests or responses side-by-side using external diff tools (VS Code / WinMerge)
• Automatic extraction and display of SOAPAction headers
• Automatic resolution of IIS Application Pool names for w3wp processes
• Visual status indicators (Green/Gray/Red) for HTTP response codes
• Real-time list filtering by URL, Method, Status, or App Name
• Export individual requests and responses to text, XML, or JSON files
• Clear all captured sessions with a single click

Installation & Usage (For Users)

This application is Portable and does not require an installation wizard or a .NET runtime installed on your machine.

1. Download the SoapProxyApp.exe file from the Releases section.
2. Important: Because this is a downloaded executable, Windows SmartScreen may block it. Before running, Right-Click the .exe file -> Properties -> Check the Unblock box at the bottom -> Click OK.
3. Run as Administrator: For the application to resolve IIS AppPool names (and to automatically install the proxy certificate), you must right-click and select Run as Administrator.
4. Click the Start Proxy button. (Optionally check System Proxy to intercept ALL computer traffic like Fiddler).
5. Click the Install Cert button.
6. Start making requests from your WCF or Web application (traffic will automatically route through the proxy and appear in the list).

What's New (Changelog)

v2.0.0

• Auto-Responder (Mocking): Create mock rules to intercept outgoing requests based on their URL, and instantly return a fake response directly from the proxy! This enables offline development, simulates edge-case server errors (e.g., 500 Internal Server Error), and allows manipulating payloads on the fly without touching the real server backend. Mocked requests are clearly marked as [MOCKED] in the session list.
• Mock in Replay: The Replay Window also evaluates your Mock Rules, allowing you to test mock responses directly via manual resends.
• Search (Ctrl+F): Added a powerful built-in Search Panel to all code editors (Request/Response Raw, Replay Window, Mock Editor). Simply click inside the code editor and press Ctrl+F to search through massive XML/JSON payloads with support for Match Case, Whole Word, and Regex.
• IIS AppPool Detection: Accurately reads process names using WMI, properly displaying the exact IIS Application Pool name (instead of generic w3wp) even for mocked sessions.

v1.9.1

• Granular Save/Load: You can now save individual or multi-selected sessions via the right-click context menu. Loading sessions now intelligently prompts whether to append to the existing list or clear it first.

v1.9.0

• Save & Load Sessions: Save captured transactions to a .sps file and load them later for offline inspection.
• Delete Transactions: Select specific transactions in the list and remove them via the context menu or by pressing the Delete key.

v1.8.0

• Replay / Resend Request: Right-click any captured session to open it in a Replay Window. Edit the URL, Method, Headers (including auth tokens), and Body, then send it again. The replayed request is automatically routed through the proxy so you can inspect the response!

v1.7.0

• HTML and Image Tabs: Added dedicated tabs for previewing raw HTML and rendering captured Images directly in the UI.
• Smart Auto-Tab Selection: Clicking a transaction now automatically switches to the most logical tab based on the Content-Type header (e.g. automatically opening the Image tab for images, or Formatted JSON for JSON responses).

v1.6.0

• System Proxy Toggle: Added a checkbox to instantly register the app as the Windows System Proxy, intercepting ALL traffic from browsers and other apps.
• Real-time Filter: Added a live search box above the session list to quickly filter out noise by URL, App Name, or Method.

v1.5.1

• Dynamic Versioning: App now automatically detects its version from assembly metadata.
• Auto-Updater: The application checks GitHub on startup for new releases and prompts the user with a direct download link.
• Admin Privileges: Embedded an pp.manifest to automatically request Administrator privileges, guaranteeing the ability to read WMI process command lines.

v1.4.0

• Diff Tool Integration: Select two sessions (Ctrl+Click), right-click, and compare them side-by-side using VS Code or WinMerge.
• IIS AppPool Parsing: Client processes named w3wp are now inspected via WMI to display their actual Application Pool name.
• SOAPAction Extraction: The SOAPAction header is now visually extracted and displayed prominently above the Request tabs.

For Developers

The application is built using C# (.NET 10) and WPF.

1. Open the solution or folder in Visual Studio.
2. Build the project (NuGet packages will be downloaded automatically).
3. Run the application.

Dependencies

• Titanium.Web.Proxy
• Newtonsoft.Json
• AvalonEdit
• System.Management