network-programmingethernetlansmbfile-sharing

Troubleshooting the network connection on a Windows 10 PC in LAN


I have a small LAN and one of the PCs (Windows 10) started to behave weird after a Windows update.

Here it how it behaves:

An example of such program is "Winpopup LAN Messenger" ( https://www.softpedia.com/get/Internet/Chat/LAN-Messaging-Clients/Winpopup-LAN-Messenger.shtml )

I checked the network advanced sharing settings and it's set like before (Turn on network discovery, Turn on file and printer sharing).

I disabled the firewall / windows defender.

With netstat -an command in cmd prompt I can see that those programs are listening to the UDP ports that they are supposed to listen to, however they don't respond to incoming requests from other machines.

I am really puzzled about this weird new behavior.

Any hints would be really appreciated.


Solution

  • I could figure it out. All the problems came from the firewall settings.

    In Windows Defender Firewall > Allow an app or feature > check both 'Private' and 'Public' for all instances of WinPopup LAN Messenger > click OK Also, the port used is 1152 and protocol UDP. This port must be opened (also in firewall).