How to install telnet client or ensure that it is installed
1. Click on the Window key on your keyboard or the Window button at the bottom left hand-corner of the screen. Then start typing Turn Windows features on or off and click on the app with the same name.
2. After waiting a little bit for all features to load, select the checkbox besides Telnet Client if it’s not checked already. Be careful not to install or enable Telnet Server (it’s a different app). Click on the OK button after checking the Telnet Client box. This will install the telnet client feature and you will be able to use it in the future.
How to use telnet to test your connectivity to your server on a specific port
1. Press the Windows key on your keyboard and type ‘cmd’. Open the Command Prompt (Desktop application).
2. The syntax for the telnet command is the following:
telnet IP PORT
e.g. telnet 18.104.22.168 1433
In the example above, telnet will try to establish a connection from your PC to the Hostway server on the specified port. Each service that is exposed to the Internet is in general associated with a port (where it listens for connections from the outside world). If you get a black screen when you issue the command (hit the ‘Enter’ key to do that), it means you can connect to the port and it is open to you.
Some well-known TCP port numbers
Web servers (Apache, IIS) usually listen on port 80.
Mail servers (Postfix, Exim, Qmail etc.) accept connections on port 25.
The default MySQL port is 3306. (This port may not be open to the Internet, which is a lot more secure, as usually the web server is on the same host as the MySQL server, so there is no need to open port 3306 to the public).
The default Microsoft SQL (MSSQL) port is 1433.
POP3 (protocol for the email retrieval by email clients such as Outlook or Thunderbird) is on 110. The secure POP3 is on 995. The IMAP port is 143 and its secure equivalent (IMAPS) is on 993.
FTP (file transfer protocol) is bound on port 21. On Linux systems, one can use port 22 for FTP commands.