I got really stuck working with some ASP code that is connecting to an ASP.NET webservice, nothing helps more than being able to see what is being returned (or not being returned in my case). This simple SOAP client on ibm developerWorks came in handy, the code is available to download.
Check out Ethereal, a powerful and free network sniffer. It understands a huge range of protocols, so it can display messages to you in a surprisingly intelligent way (i.e. rather than seeing a stream of bits, you can see “HTTP: REQUEST /index.htm” or “AIM: ‘Joe’ logged in”).
I just started using it this year, we used it at work last week to diagnose some DNS server issues and also figure out some unhelpful error messages from Outlook… it is an *incredibly* useful addition to the toolbox!
It stripped my <A> tag… that’s not very nice…
http://www.ethereal.com