Wireshark - Wireshark is a network protocol analyzer for Unix and Windows. It lets you capture and interactively browse the traffic running on a computer network.
SmartSniff - SmartSniff is a packet sniffer that capture TCP/IP packets and display them as sequence of conversations between clients and servers.
netcat - Netcat is a featured networking utility which reads and writes data across network connections...
Ettercap - Ettercap is a suite for man in the middle attacks on LAN.
Fiddler - Fiddler is a debugging program for websites.
Ethereal - Ethereal® is used by network professionals around the world for troubleshooting, analysis...