is a free and open-source packet analyzer. It is used for network troubleshooting, analysis, software andcommunications protocol development, and education. Originally named Ethereal, in May 2006 the project was renamed Wireshark due to trademark issues.
Wireshark is very similar to tcpdump, but it has a graphical front-end, and many more information sorting and filtering options. It allows the user to see all traffic being passed over the network (usually an Ethernet network but support is being added for others) by putting the network interface into promiscuous mode