wireshark - is a network protocol analyzer for Unix and Windows
tshark is a console version of wireshark
iperf - traffic generator is a commonly used network testing tool that can create
tcp and
udp data streams and measure the throughput of a network that is carrying them
packEth - is a Linux GUI packet generator tool for ethernet. It allows you to create and send any possible packet or sequence of packets on the ethernet
tcpdump - dump traffic on a network
tcpreplay - gives you the ability to use previously captured traffic in Libcap format to test a variety of network devices. It allows you to classify traffic as client or server, rewrite Layer 2, 3 and 4 headers and finally replay the traffic back onto the network and through other devices such as switches, routers, firewalls, NIDS and IPS's. Tcpreplay supports both single and dual NIC modes for testing both sniffing and inline devices.
vlc - is a free and open source cross-platform multimedia player and framework that plays most multimedia files as well as DVD, Audio CD, VCD, and various streaming protocols
mplayer - is a movie player for Linux. Supports reading from network, dvd, vcd, file, pipes, and v4l.
Packet builder - enables creating custom network packets; users can use this tool to check their network protection against attacks and intruders.Colasoft Packet Builder includes a very powerful editing feature. Besides common HEX editing raw data, it features a Decoding Editor allowing users to edit specific protocol field values much easier
PuTTY - SSH and telnet client
nmap - is a free and open source utility for network exploration or security auditing.
xchm - .chm viewer