How do I see the raw HTTP request that the HttpWebRequest class sends?

Question

I know you are all going to answer "use a debugging proxy server like Fiddler" but it's not that simple.

Here's my situation: I have some code that runs on a server, in an ASP.NET page code-behind (aspx.cs), which (among other things) establishes a connection to another server, grabs some stuff, and then formats it and returns it to the browser.

The problem is that the other server is doing the wrong thing, and so I want to be able to pass a debugging flag into the page (via the query string, e.g. ?debug=true) so that it will print out the completely raw HTTP request that it is sending to the other server so I can see what the heck is wrong. This code is running in several places so I want to be able to just pass in this flag on dev, staging, or production and just see the request, without having to figure out whether the production servers can talk to some proxy server that exists somewhere, etc.

You would think that it would be easy to do this, right? So I feel like I'm crazy or something but I looked at the reference for HttpWebRequest and its parent class WebRequest and -- nothing. No can do. You would think Microsoft would have thought of this. The closest thing is that you can access the "Headers" collection but when I tried it, it omitted some really important headers like "content length" -- so it must be "lying" to me (I know it's lying, because I know for a fact that the remote server is returning a 200 status -- the request is successful, it's just returning bad/different/wrong data)

Here is the asked-for code example:

HttpWebRequest req = (HttpWebRequest)WebRequest.Create("http://www.whatever.com");
req.Method = ... whatever ...;
... other setup for the request ...
/* At this point we are about to send the request.
   What does the raw HTTP request look like? */
HttpWebResponse resp = (HttpWebResponse)req.GetResponse();

Answer 1

You can use a network traffic sniffer like wireshark.

This is not a debugging proxy, but will sniff all traffic and let you see the raw requests/responses.

Answer 2

Another suggestion. Implement your own web proxy, and set your request to use it with WebRequest.Proxy. Then you should be able to extract the traffic from the proxy instance.

Edit: update for links.

Answer 3

You can use System.Net tracing mechanism to see the raw HTTP requests sent on the wire. See how to create a system.net trace logfile. You can also add your own tracelistener to the process.

Answer 4

You say that you think .NET is lying to you, and the specific example you give is that the header Content-Length is missing from the HTTP response.

But the header Content-Length is not required from an HTTP response. In fact, if the body of the response is in any dynamic, and if its length is not known in advance, then it is highly likely that the Content-Length header will be omitted!

Answer 5

Hi -- answering my own question here, because I thought of another way to do it. Basically the idea is -- you re-point the HttpWebRequest to a page that logs the incoming raw HTTP Request. In other words set up a custom HTTP handler as per this forum post:

http://forums.asp.net/t/353955.aspx

And then change just the URL in the HttpWebRequest to point to this new endpoint, but keep all other elements of the request the same. Write the result to a file or something and you're golden.