In many cases, you may in trouble because email can not be sent out by your web application, can not connect to FTP server, can not remote desktop to an external server or simply can not access to a particular service which is running on a remote server. The first thing you need to investigate the issue is determine if the port for that service is open or not.
As you know, every service run on a server via a port. And for some reasons, your ISP (Internet service Provider) block that port or if your server stands behind a firewall, the port may be blocked as well.
So, in order to check if a particular port (ex: port 25) is open or blocked, follow simple steps below:
- 1. Open Command Prompt by clicking Start then type cmd then press Enter or pressing Windows Key + R
- 2. In the Command Prompt, type telnet rapid-tools.net 25. If port 25 for SMTP service is running and allow external connection, you should see something like this:
telnet port 25
- 3. If the port is blocked or not available, for example: telnet google.com 25, it will say: ‘Connecting To google.com…Could not open connection to the host, on port 25: Connection failed’ and shows something like this:
telnet port 25 is blocked
Note: if you’re receiving an error message “‘telnet’ is not recognized as an internal or external command, operable program or batch file.” with the telnet command above, you need to Enable Telnet Client in the Windows Features.
