Wireshark is a free and open-source packet analyzer. It is used for network troubleshooting, analysis, software and communications protocol development and education.
Wireshark is cross-platform, using the Qt widget toolkit in current releases to implement its user interface, and using pcap to capture packets. Additionally, a terminal-based (non-GUI) version, TShark, is available. Wireshark, and the other programs distributed with it such as TShark, are free software, released under the terms of the GNU General Public License.
Wireshark is open source and available to all users.