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An easy way to see if the App is running 'avahi-daemon' and advertise service/hostname correctly, One can issue "ps aux | grep 'avahi-daemon' " to see if it is running. Or one can issue "sudo systemctl status avahi-daemon" to see the 'avahi' status. Then install the 'avahi-browse' by "sudo apt install avahi-utils". The 'avahi-browse -a" command output should display the hostname, service, etc info:
ubuntu@ubuntu:/etc/avahi$ avahi-browse -a | grep server
+ eth0 IPv4 ubuntu-4321-http-server [00:16:3e:00:01:03] Workstation local
+ lo IPv4 ubuntu-4321-http-server [00:00:00:00:00:00] Workstation local
Local DataStore Protocol Scheme
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