Port Probe 

This tool allows you to test whether a port is open on a server it allows you to do this one of two ways. You can test the port is open by specifying the port using it's URL or you can test the port is open by specifiying the port and its IP address. The tool will return whether the port is open or closed this can be a very useful tool in testing the security of your network. Port 80 is the HTTP port and port 53 is the DNS port these must be open or your connection will not work add 448 to that for cryptography then 25, 110, 587, and 990 for email. Generally speaking only the ports of the services you need should be opened all the others should be closed.