Wireshark (formerly known as Ethereal) is a top open source product that allows you to capture (or sniff) packets on a LAN (local area network) in order to analyze the network traffic.
Once you turn on Wireshark's packet sniffer - it immediately starts collecting data off the network, decoding packets and displaying the results on screen.
Filters can be added to make sure that unwanted traffic is not processed, thus making it easier to get an overview of the traffic that you are interested in.
Wireshark is able to detect and decode more than 50.000 different network protocols on all network layers. All of this on virtually any physical network connection 100Base-T, ATM, Token Ring, etc.
Wireshake is truly a worthy competitor to all commercial packet sniffers and network analyzers. Wireshark was the new project name from mid 2006 following Ethereal.
Wireshark is the world's foremost network protocol analyzer, and is the de facto (and often de jure) standard across many industries and educational institutions.
Wireshark development thrives thanks to the contributions of networking experts across the globe. It is the continuation of a project that started in 1998.