Wireshark Tutorial
Wireshark is a free program for analyzing and graphically presenting data protocols (sniffer). Such data protocols are used by computers on various communication media such as the local network or USB. Capturing the communication can be useful for troubleshooting or evaluating the content of the communication. Wireshark displays both the protocol headers and the transported content during a capture. The program relies on the output of small helper programs like pcap or usbpcap for the graphical presentation, in order to capture the communication content on the respective transmission medium. [wikipedia] ...