There are 4 places the port may be closed
- Your ISP
- The Endpoint on Azure. Make sure that is open
- Firewall on the OS, e.g. IPTables in your case
- The Application
Step 1
Allow EVERYTHING through IPTables. Basically take down your firewall. Try telnet now. If it works it is an IPtable misconfiguration.
Step 2
Telnet on your own VM to see if the application has the port open. If yes, then it is a firewall blocking. If no, your application isn't opening the port.
Step 3
Use http://www.canyouseeme.org/ to check ports are open outside of your ISP.
If this works, its your ISP. If it doesn't it is your endpoint configuration on Azure.