NetSorcer
NetSorcer was originally made to help me with an assignment for a networking class. The small application allows you to send completely customized IP, UDP, ICMP and RAW packets to the network. You can specify every field (with no error checking) of the packet as well as send data. It is written in Objective-C and Cocoa so it is Mac OS X only at this point. Of course the socket code would work on any POSIX based system but a front end would need to be re-written.
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