A number of ways you could do this:
One way is to use telnet. From outside of the LAN (from your home as an example) launch terminal and telnet to the relevant port. If we use server.example.com as the hostname of your server or 100.100.100.100 as the external IP address of your server the command would look like this:
telnet server.example.com 2195
telnet 100.100.100.100 2195
It will either say connected or it will refuse the connection. Change the port number to test the other ports.