How to drop TCP connection without killing process?

[Larry Cook]

Does anyone know of or have a utility that can drop TCP connections without 
killing the process that made the connection?

I'm trying dsniff/tcpkill and hunt, but both need to see some traffic first. 
Either there's no keep-alive packets being sent on the connection, or I'm not 
setting the filter correctly.

Suggestions on other utilities or instructions on how to see TCP keep-alive 
packets using a tcpdump expression would be helpful.

Thanks,
Larry