Telnet is a useful tool that you can use to test the network connection to your server on a specific port. (The telnet protocol can do many other things as well.)
First, you will need to open a command prompt application.
- Open your Finder (the blue face).
- Go to your Applications.
- Open the Utilties folder.
- Open the Terminal application.
- Go to Start.
- Open Run. (The Run field is automatically shown in Windows Vista and higher.)
- Type cmd and press Enter.
You should now be looking at a command prompt, which looks like a box where you can type something. The general format of a telnet test is as follows. Type the following, then press Enter:
telnet example.com 25
Where EXAMPLE.COM is the domain or IP address of the server that you want to reach, and 25 is the port that you want to test.
A response of 220 or Connected indicates a successful connection to the server.
A connection timeout or response of Unable to connect indicates that your computer is not able to connect to the server on that port. This indicates that the port may not be open on the server, or that the network connection may be blocked.
- 25 is the standard outgoing port, and most likely to be blocked.
- 587 is the alternate outgoing port, and may not work with your Jumpline server.
- 465 is the SSL encrypted outgoing port.
- 143 is the standard incoming IMAP port.
- 993 is the SSL encrypted incoming IMAP port.
- 110 is the standard incoming POP port.
- 995 is the SSL encrypted incoming POP port.
- 21 is the standard FTP port
- 22 is the Secure FTP port
- 22 is the standard SSH port
- 80 is the standard HTTP port (for viewing web pages)
- 443 is the SSL encrypted HTTPS port