Nmap - Nmap Free Security Scanner, Port Scanner, & Network Exploration Tool. Download open source software for Linux, Windows, UNIX, FreeBSD, etc.
PortMapper - Do you need to map a specific TCP or UDP port on your machine to another port on another machine?
SolarWinds Network Configuration Manager - SolarWinds is a leading provider of powerful and affordable IT infrastructure management software. Make IT look easy.
netcat - Netcat is a featured networking utility which reads and writes data across network connections...
Cisco Network Assistant - Cisco Network Assistant simplifies wired and wireless network management, and provides critical product information using Cisco Active Advisor.
Komodia Relay - Free open source tool to perform TCP based session relay