I need to validate some network connectivity from machine X to a Windows 2003 Server machine. To be able to do so I'm looking for a simple utility that I can run on the Windows 2003 server that will listen on a specified port. It does not have to do anything else. When it listens on the specified port I can do a telnet to that port from machine X and check if all firewalls are open.
The Windows 2003 Server machine is already a production machine so I cannot install all kinds of stuff. At this stage we want to ensure that all network connectivity is in place before we do the installation of the 'real' application that will listen that port (don't want to wast time debugging network connectivity issues when we do the actual deployment of the new application.
The utility should be a simple command line utility that does not require any installation.
What utilities do you recommend?