Cannot open port in Azure Virtual Machine

Question

I have tried everything and am now exhausted!
Hoping someone can step me through the process to open a port on a Windows VM.
Done so far:

1. Port 3389 was already open and working fine
2. I tried to open ports 21, 3306 and 5055
3. Opened the ports in NSG
4. Open Ports on Windows firewall.
5. When didn't work have completely disabled Windows firewall

Answer 1

Hi @Mike Fairley
as very well demonstrated by Andrea Baumgarten, it looks like your external connection on port 5055 is working fine, so I think of two hypotheses

1 - there is a port source block, like outbound of your client (some ISP block the ports)

2 - there is something else preventing the connection, such as an antivirus

Can you do an internal and external telnet test? like

telnet localhost 21
telnet localhost 5055

telnet 47.x.x.x.x 21
telnet 47.x.x.x.x 21

If telnet gives an ok status, it means that the port is listening and maybe only the service is not responding. You can also use PowerShell to test port, like

Test-NetConnection 8.8.8.8 -port 53

Or an online tool, like:

https://www.yougetsignal.com/tools/open-ports/

Testing an online tool can help eliminate source client or ISP

Answer 2

Hi @Mike Fairley ,

NSGs could be associated with the VM and/or with a subnet.
If there is more than one NSG in the game the security rule sets must match in both NSGs.

If you have 2 NSGs it looks like this:

You can check the effective security rules applied to the VM by clicking on Effective security rules. The result should look like this:

You could run a Connection Troubleshoot test to get more details:

Are you able to connect via Port 21 from a VM in the same subnet of the affected VM?
Please verify the affected VM is listening on Port 21.

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(If the reply was helpful please don't forget to upvote and/or accept as answer, thank you)

Regards
Andreas Baumgarten

Answer 3

Thanks for the detailed answer and the effort of including screen captures.
I have a very simple lab server. I have only one NSG.

Here are the effective rules

Here is my connection diagnostic

Still not able to connect from outside using public ip.

Answer 4

Sorry - I have now marked your answer. Thanks for your help.