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Port 774 (acmaint-dbd)

IANA assigns port 774 to acmaint-dbd: IANA assigned this well-formed service name as a replacement for "acmaint_dbd"..

Well-known (system) port, 0-1023 UDP

Port 774 is normally used over UDP; the checker tests TCP only, so a "filtered" result does not mean the UDP service is down.

IANA assignment

Service nameProtoDescriptionAssigneeReference
acmaint-dbd UDP IANA assigned this well-formed service name as a replacement for "acmaint_dbd". - -

Check what is listening on port 774

Linux: UDP 774
sudo ss -ulnp 'sport = :774'
Linux / macOS: which process owns the port
sudo lsof -nP -i :774
Windows (Command Prompt)
netstat -ano | findstr :774
Windows (PowerShell)
Get-NetUDPEndpoint -LocalPort 774

Test it from outside

UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 774

Block port 774 in the firewall

ufw
sudo ufw deny 774/udp
iptables
sudo iptables -A INPUT -p udp --dport 774 -j DROP
nftables
sudo nft add rule inet filter input udp dport 774 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 774' -Direction Inbound -Protocol UDP -LocalPort 774 -Action Block

Related ports

754tell767phonebook775acmaint-transd777multiling-http

All port numbers · Open port checker
Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.