Wireshark

Skype traffic can be analyzed using the protocol analyzer Wireshark. A Skype session starts with a UDP connection to a Microsoft Node, listening on port 33033. After the initial negotiation via UDP, an obfuscated TCP session to the same node starts.

Download and compile

Skype support in Wirshark is still under development and not yet included in a precompiled version, so in order to have it, you need to get the recent sources from the repo:

 svn checkout http://anonsvn.wireshark.org/wireshark/trunk wireshark

and compile them yourself:

 automake --add-missing