I'm working on an orchestration that's retrieving some data from a Java servlet.  The servlet takes a parameter string via HTTP post and returns POX (plain old XML, no SOAP here).  I was having trouble getting a valid response from the servlet when I was sending some test messages and wanted to see what my messages were looking like as they went across the wire.  Normally I was using WCF, I'd setup message logging, but since that's obviously not an option with the HTTP adapter, my thoughts turned to Fiddler. 

A quick Google search turned up some promising results.  The posts I read all referred to using Fiddler with the SOAP adapter, but I thoght I could apply the same ideas to the HTTP adapter.  This led me to try setting the following context properties:

HttpRequestMessage(HTTP.UseProxy) = true;
HttpRequestMessage(HTTP.ProxyName) = "127.0.0.1";
HttpRequestMessage(HTTP.ProxyPort) = 8888;

I rebuilt my orch, gac'd it, bounced my host and tried submitting a test message.  Fiddler was running but I didn't see any traffic show up.  I tried fully undeploying/redeploying my application and still, no traffic in Fiddler.  I was starting to think that BizTalk was ignoring the proxy settings.  To confirm this, I closed Fiddler and submitted a test message.  Sure enough, the orch ran to completion, proving that BizTalk was ignoring the proxy settings.

I went back to my orch to see if there could be any other context proprties I needed to set.  I saw one that looked promising:  HTTP.UseHandlerProxySettings.  I set this to false, rebuilt my orch and this time when I submitted, I got an error message, which made sense, I didn't have Fiddler running.  I started up Fiddler, submitted another message and there it was, my HTTP traffic, just as I hoped.  And, I was quickly able to figure out what the problem was...I had forgotten to set HTTP.ContentType to application/x-www-form-urlencoded.