Here is a quick guide on how to verify that Ports 443 & 80 are open and listening for traffic from Datalink 3 & Datalink 4. The Windows and Linux OS instructions are as follows:
  

Windows 

1. Open the Windows Start Menu or press the Windows button on your keyboard.
2. Find and open the Command Prompt application. You can find it quickly by searching for cmd in the Start Menu.
3. When the Command Prompt window opens, enter the following command: netstat –an find “LISTENING”
4. The Command Prompt should display all ports are their listening state.

Linux

1. Open the Linux Command Prompt (Linux should have a similar Command Prompt interface to Windows OS).
2. When the Command Prompt window opens, enter the following command: netstat – an | grep –i listen | grep ‘:80\|443
3. The Command Prompt should display TCP connections and their listening state.

Additional Troubleshooting with Telnet

1. Install and open Telnet.
2. Click Start and then Control Panel.
3. On the Control Panel home page, click Programs.
4. In the Programs and Features section, click Turn Windows features on or off.
5. If the User Account Control dialog box appears, confirm that the action it displays is what you want, and click Continue.
6. In the Windows Features list, select Telnet Client then click OK.
7. Open the Command Prompt and use the following command: input telnet dl-customername-manager.apptio.com ###
   • Replace ### with the port number you wish to test.
8. When a connection is made to a listening SSL port, the Telnet session will show a blank flashing cursor, as if the server is waiting for input.
9. After several seconds, or if you press any keys, the Telnet client will display the following: Connection to host lost.
10. A connection to a server that is not listening on SSL immediately returns the following message: Could not open a connection to host on port ### : Connect failed