SmartSniff - SmartSniff is a packet sniffer that capture TCP/IP packets and display them as sequence of conversations between clients and servers.
socat - socat is a relay for bidirectional data transfer between two independent data channels.
tcpdump - tcpdump is a common packet analyzer that runs under the command line.
Packet Sender - Packet Sender can send and receive UDP, TCP, and SSL on the ports of your choosing.
netcat - Netcat is a featured networking utility which reads and writes data across network connections...
Portfwd - Portfwd, Port Forwarding Daemon, stands for port forwarding daemon.