hping is a command-line oriented TCP/IP packet assembler/analyzer.
The interface is inspired to the ping(8) Unix command, but hping isn't
only able to send ICMP echo requests. It supports TCP, UDP, ICMP and
RAW-IP protocols, has a traceroute mode, the ability to send files
between a covered channel, and many other features.
While hping was mainly used as a security tool in the past, it can be
used in many ways by people that don't care about security to test
networks and hosts. A subset of the stuff you can do using hping:

	- Test firewall rules
	- [spoofed] port scanning
	- Test net performance using different protocols,
	  packet size, TOS (type of service) and fragmentation.
	- Path MTU discovery
	- Files transfering even between really fascist firewall rules.
	- Traceroute like under different protocols.
	- Firewalk like usage.
	- Remote OS fingerprint.
	- TCP/IP stack auditing.

WWW: http://www.hping.org/