Packet-Crafting

Hping is the most popular packet crafting tool. It is a free tool.  With Hping you can assemble and send custom ICMP, UDP, TCP and IP packets. Hping is supported various platforms likeWindows, Linux, MacOs X, etc. You can download Hping, below.

http://www.hping.org/

Ostinato is an open source network packet generator and analyzing tool. Ostinato supports many common protocols. With Ostinato , you can modify any protocol. You can download Ostinato, below.

http://ostinato.org/

Scapy is a  Python based Packet Crafting tool. With Scapy , you can modify many common protocols.  Scapy can be used for scanning, tracerouting, network discovery etc. You can download Scapy, below.

http://www.secdev.org/projects/scapy/

packETH is  a Linux GUI tool for ethernet. With packETH you can create and modify many common protocols. You can download packETH, below.

http://www.secdev.org/projects/scapy/

Netcat is an user friendly Packet Crafting tool. The previous name fof this tool was Hobbit.  With Netcat you can create any kind of network connection with its port binding. You can download Netcat, below.

http://nc110.sourceforge.net/