I was recently asked how to open ports within the firewall. Since it's been quite a while since I've had to do something like this, I took the time to relearn and write some documentation.

In this tutorial, I'll cover how to open a port on your server and test that it is open. More specifically, we will open port 9090.

Please note! This tutorial assumes you have a VPS Server or a Dedicated Server, that you have root access, and that you know how to connect to your server vis SSH.

Step 1: Check if the port is open already

The first thing we want to do is test using telnet to ensure port 9090 is not already open. Please note that you may need to enable telnet in Windows first.

(The below was ran from cmd.exe in Windows 7)
C:\Users\Brad>telnet yourdomain.com 9090
Connecting To yourdomain.com...Could not open connection to the host, on port 9090:
Connect failed

As you can see, the connection failed.

Step 2: Open the port

To open a port, first open for edit your APF configuration file - /etc/apf/conf.apf:

(The below was ran within PuTTY after connecting vis SSH)
root@vps### [~]# vim /etc/apf/conf.apf

Then, find the following lines and add the port in question:

# Common ingress (inbound) TCP ports

# Common ingress (inbound) UDP ports

After editing the file and adding the ports, restart APF:

root@vps### [~]# service apf restart

Step 3: Test again to see if the port is open

Now that APF is restarted, we can once again use telnet to test if the port is open:

(The below was ran from cmd.exe in Windows 7)
C:\Users\Brad>telnet yourdomain.com 9090
Connecting To yourdomain.com...
220-vps###.inmotionhosting.com ESMTP Exim 4.80 #2 Fri, 17 May 2013 05:11:39 -0700
220-We do not authorize the use of this system to transport unsolicited,
220 and/or bulk e-mail.
As you can see, instead of the Connect failed message, we received the greeting from the application running on port 9090. Congratulations, you now know how to open a port on your server using ssh!

Please note! If you do not have any services running on your server listening to the port in question, you won't get a response when you do a telnet test. In the above scenario, we setup exim to listen on port 9090, which is why we received a response.

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