Fiddler and HTTP Proxy Chaining

[TonyValenti]

We often use fiddler to monitor http traffic between our app and the internet.

Our app detects the system proxy and uses it, which is fiddler when fiddler is running.

This works great when a proxy isn't required.

Sometimes, however we need our app to communicate through a specified proxy.

How do we chain proxies together? (Ie. Use fiddler and pass the request to Proxy X).

Alternatively, is there a fiddler replacement we should use that would still let us monitor requests that are sent directly to a proxy?

[huoyaoyuan]

You need to inform fiddler to use upstream proxy. I've written three versions of solutions in the past, for games that must use proxy:

FiddlerCore based:
https://github.com/huoyaoyuan/AdmiralRoom/blob/97a300a933cefae9ac6606c7207e4b3022f5573e/AdmiralRoom/Officer/Staff.cs#L39-L50
https://github.com/huoyaoyuan/AdmiralRoom/blob/97a300a933cefae9ac6606c7207e4b3022f5573e/AdmiralRoom/Officer/Staff.cs#L61-L75

A custom HTTP proxy that uses ASP.NET component for HTTP parsing:
https://github.com/amatukaze/Nekomimi/blob/1b2544c43c7ddfa78871bf0f454d42e46435267e/src/Nekomimi/ProxyServer.Handle.cs

Or, just register a custom HTTP handler for your http client that listens requests. This requires full control of http client usage, however.

[TonyValenti]

Thanks for the suggestion but I'm hoping for something that doesn't involve configuring fiddler.

I have full control over my httpclient so I can send whatever headers are necessary.

I'm looking for a way to monitor the requests/responses without having to configure something upstream. I'd like to be able to do everything from within my app.

By the way, my app is a desktop based app that runs on a person's PC.

[huoyaoyuan]

In this case, why do you need Fiddler in the first place? You can insert a DelegatingHandler to your HttpClient and do logging etc. I'd expect there to be some factories already doing so.

[TonyValenti]

We don't need fiddler specifically but it has a good interface that makes it easy to view/search/filter data in real time without having to maintain log files.