A couple of Command line utilities one winsock based the other dotNet4. to ping a specific port.
Usage mfpping Host|IP port
They both return;
0 Successful Connection
256 Connection Timeout
512 Other Error e.g. Incorrect syntax.
I use this in a couple of places on my mail server to ensure Anti Virus is up before bringing up the mail server and also for testing port 554 on App-V 4 streaming servers.