How to open 8420, 8421, 8422, 8423

Question

Dears,

Please, I need support if anyone give me some idea about this ports [8420, 8421, 8422, 8423 ]. As I tried to open through the windows firewall rules but i can't telnet as well I make the firewall OFF but also I can telnet the mention ports, please if anyone have idea how to open it ?

I appreciate you support ..

Thanks

Answer 1

Hi,

Thank you very much for the reply. To double confirm that we can reach the application/progrom (listening on a specific port) through the windows firewall, we can do the following:

1) let a program to listen on this port (we take terminal server as an example since it's easy to change the port via registry, and you may test with any program you like)
2) create a rule to allow the connection (the steps mentioned above)
3) from another computer, run some test tool (for example, telnet client, Test-NetConnection PS cmdlet, scanport tool, etc.) to test the connection for double confirmation.

Here's the detailed steps for the example

1. change terminal server port (default value is 3389) to the port we desired, for example, 1000, via registry, reboot the computer to make the changes to take effect
   Registry:
   HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Terminal Server\WinStations\RDP-Tcp\PortNumber
   PortNumber: 0x00000d3d (3389) to 0x000003e8 (1000)
   

2) we can run netstat -abn command to ensure the program is listening on this port

If not found, we may need to enable remote desktop first

3) from another compouter, test the connection with any tool you like

test-netconnection -computer 172.17.12.59 -port 1000 -informationlevel "detailed"

Hope the above informaiton helps.

Alex
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Answer 2

Hi,

Here's the step to open ports in windows firewall.
Note: we cannot telnet the opened ports until there is a program/service which is listening on these ports.

1) make sure windows defender firewall service is running

2) open network and sharing center, windows defender firewall, advanced settings.

3) create a new inbound rule

3-1) choose protocol and ports

3-2) allow the connection

3-3) select the profile

Hope the above informaiton helps.

Alex
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Answer 3

@AlexZhu-MSFT

Hi ,

Thanks to you for useful information : " Note: we cannot telnet the opened ports until there is a program/service which is listening on these ports." ,I like this informative information .

for the firewall rule I did as your explanation , But how to test trial a program/service to verify and proven this port is open ?