Check if a port is open

Hello,

I'm looking for a way to see if a specific port, on a specific IP address is
available, or will respond. I want to write a spiffy little HTA that my
users can use at hotels and customer sites to determine if their VPN client
will work, or rather if the ports for the VPN client are open.

Any suggestions or libraries, or anything would be greatly appreciated.

Thank you.