Wireshark which was originally known as Ethereal is a network support product which allows you to sense packets on a LAN and use them for the analysis of network traffic. The packet sniffer of Wireshark has to be turned on by the user as a result of which the sniffers start collecting packets on the network and displaying them on the screen.
If your interest is only in specific type of packets, filters can be introduced so that you collect only those packets which meet your criteria. The software is very versatile and is able to capture and analyze packets conforming to over 50000 network protocols. It also supports various physical connections such as 100Base-T, TokenRing, and ATM etc.
In terms of performance and comprehensive features, Wireshark gives a very good competition to the other commercially available products. Being the Open source software, Wireshark can be freely downloaded and used without any licensing instructions. You can even change the code to meet your special requirements provided that the changed code is put back into the Open space.
Continued support of the user community has enriched Wireshark to a great extent with the continuous supply of additional features. The software is more useful for the professional community who is able to understand the subject rather than the average user who may not know much about the packet analyzers.