Sometimes I need to observe HTTP communication between my and another machine. I usually use Eclipse’ integrated TCP/IP monitor for it’s simple and does its job well but today for a large response it just displayed “The HTTP content is too large to display.” so I started searching for alternatives and found the Grinder TCPProxy, written in Java and distributed under the BSD license.

Grinder is a Java load testing framework and the proxy is just a part of it. Here is how you would start the proxy to forward local port 6080 to the remote address example.webservices.com:80 and log the HTTP communication into a file:

java -cp lib/grinder.jar net.grinder.TCPProxy -console -localhost 127.0.0.1  
-localport 6080 -remotehost example.webservices.com -remoteport 80 > http.log

The optional flag -console makes it  to display a window for shutting it down cleanly (likely unnecessary under Linux/Mac). When you want it to log just into the console, add -colour for nicely colored output.

Run it with -? to see all the available options.

From http://theholyjava.wordpress.com/2011/07/28/simple-logging-http-proxy-with-grinder/