TcpCatcher Home Page

Overview

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:

turn on 'Catch Mode' and debug step by step the client-server communication, each packet intercepted being friendly editable
with few clics, define an automatic transformation on each packet going through with the hook builder (remove or overwrite HTTP headers, search&replace HTTP contents) or plugin your own java code for any other on the fly modification (see javadoc)

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