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TcpCatcher is a free TCP, SOCKS, HTTP and HTTPS proxy monitor server software.
  As a developer tool, TcpCatcher will let you debug any client-server application by displaying TCP packets.
As an educational tool, TcpCatcher will help understanding any TCP based protocol.
Since HTTP has became the most commonly used protocol, TcpCatcher provides a large tool box for helping you debug any HTTP based conversation :
  • records all traffic between your browser and the Internet. HTTP packets, often chunked and zipped at network level, are reassembled, their content is deflated and presented in a convenient way
  • HTML, JS, CSS contents appears pretty printed and can be easily saved
  • XML (like SOAP messages), Adobe Flash AMF and JSON payload formats are decoded and loaded in a tree view
  • images captured at network level are displayed
  • HTTP headers definition pops up
  • monitors servers response or ping time, upload/download rates, port scanner
  • simulate slow connection and packet loss
Unlike any other tools, TcpCatcher has the great ability of letting you interfere in the communication at proxy level:

TcpCatcher can let you debug, interfere or log an SSL communication in plain text

Multithreaded and bundled as a lightweight executable java jar, it is fast and portable and it has many extra features like searching, sorting, filtering, diffing, dec/hex packet editor to help you analyze captured traffic.

TcpCatcher is fully functional on Windows, Mac OS X, Linux,..anywhere a java runtime is installed.

Download latest version (v2.30.1, released on May 18th, 2014), Firefox Add-On now and go to Tutorials section for sample fun use cases.

Some HTTP captured traffic | Double click on one row to open packet detailed view