SmartSniff - SmartSniff is a packet sniffer that capture TCP/IP packets and display them as sequence of conversations between clients and servers.
PortMapper - Do you need to map a specific TCP or UDP port on your machine to another port on another machine?
tcpdump - tcpdump is a common packet analyzer that runs under the command line.
netcat - Netcat is a featured networking utility which reads and writes data across network connections...
Packet Sender - Packet Sender can send and receive UDP, TCP, and SSL on the ports of your choosing.
Komodia Relay - Free open source tool to perform TCP based session relay