ProxyView is a simple proxy server which relays TCP/IP[v4] connections from an IP:port defined on the commandline to another address:port. It dumps to the console all the data which arrives on the client and server sockets. It is a proxy for programmers designed to makes debugging TCP/IP software easier.
The first widely used, long term network monitoring tool on the Internet. I created it in 1995 and still update it regularly as people send in patches.