IANA assigns port 1561 to facilityview.
sudo ss -tlnp 'sport = :1561'sudo ss -ulnp 'sport = :1561'sudo lsof -nP -i :1561sudo netstat -tlnp | grep ':1561 'netstat -ano | findstr :1561Get-NetTCPConnection -LocalPort 1561 -State Listen | Select LocalAddress,OwningProcessnc -vz -w 5 HOST 1561Test-NetConnection HOST -Port 1561nc -vzu -w 5 HOST 1561sudo ufw deny 1561/tcpsudo iptables -A INPUT -p tcp --dport 1561 -j DROPsudo nft add rule inet filter input tcp dport 1561 dropNew-NetFirewallRule -DisplayName 'Block TCP 1561' -Direction Inbound -Protocol TCP -LocalPort 1561 -Action Blocksudo ufw deny 1561/udpsudo iptables -A INPUT -p udp --dport 1561 -j DROPsudo nft add rule inet filter input udp dport 1561 dropNew-NetFirewallRule -DisplayName 'Block UDP 1561' -Direction Inbound -Protocol UDP -LocalPort 1561 -Action BlockAll port numbers · Open port checker
Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.