I've been working on this program for a while: the Connection Debug Utility!
It's a multi-platform, multi-purpose, java-based networking tool with a built in tcp connection utility, tcp server utility, and port scanner, with more stuff on the way. Tested on Windows, Mac, and Linux.
I'm currently working on expanding and improving it, and will post the source for it soon enough. It is compiled for Java 6 so older machines won't have problems with it.
Screenshots of it:


It's completely free and open-source, download:
http://randomsite.net78.net/testing/upload/CDU.rar (currently version 0.1.0)
Download, extract, run ConnectionDebugUtility.jar, and enjoy!
Feel free to post comments, request, and bugs of any sort here!
Features I'm planning to add:
- UDP packet crafter
- UDP server
- ICMP packet crafter scratch that, java seems to be lacking in ICMP abilities...
- Multicast packet crafter
- HTTP request crafter
- Options to send/recieve packets in hex format
- Host resolution and mass IP scanning
- and more...
- WallShadow <3




