Having misspent years in the trenches of async, LU6.2, Netbios, token ring, and other now-obsolete data comm protocols and interfaces, I’m quite happy that nearly everything now flows over TCP/IP rivers.  Among many other things, this standardization has led to a seemingly endless supply of good tools.

It’s not often that I have to look into the traffic between Point A and Point B, but when I do, I’ve typically used simple tools like PocketSoap’s TcpTrace, pcap-based stuff like ngrep and tcpdump, or sniffers like Wireshark or Solarwinds.  Years ago, I tried Eric Lawrence’s Fiddler, but put it aside because I needed Linux tools.  But I recently needed to debug traffic under Windows, so I gave Fiddler’s successor, Fiddler2, a try.  And I’m glad I did.

Fiddler2 has a dizzying array of features while being very easy to use.  For me, I just needed it for live capture and display of HTTP packets between my client and server.  It doesn’t require manually modifying ports to sit in the middle (it proxies automatically), and it captures data for all sessions.  You can view captured data in every format imaginable, build or modify requests and responses directly from the tool, and set breakpoints and run scripts.  A very nice feature is that it can decrypt HTTPS traffic by using its own cert.  Gone are the days (under Windows, anyway) when I have to switch my HTTPS/SSL services to HTTP for tracing.

It does require configuration steps to use with non-WinINET apps (like PHP), localhost, background services (like IIS), and SSL, but these are straightforward and well-documented.

I’m happy I returned to the Fiddler family, and Fiddler2 will likely remain my tracing proxy of choice for Windows work.  At least until Fiddler3 comes along.