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Port 775 (acmaint-transd)

IANA assigns port 775 to acmaint-transd: IANA assigned this well-formed service name as a replacement for "acmaint_transd"..

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

Port 775 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-transd UDP IANA assigned this well-formed service name as a replacement for "acmaint_transd". - -

Check what is listening on port 775

Linux: UDP 775
sudo ss -ulnp 'sport = :775'
Linux / macOS: which process owns the port
sudo lsof -nP -i :775
Windows (Command Prompt)
netstat -ano | findstr :775
Windows (PowerShell)
Get-NetUDPEndpoint -LocalPort 775

Test it from outside

UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 775

Block port 775 in the firewall

ufw
sudo ufw deny 775/udp
iptables
sudo iptables -A INPUT -p udp --dport 775 -j DROP
nftables
sudo nft add rule inet filter input udp dport 775 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 775' -Direction Inbound -Protocol UDP -LocalPort 775 -Action Block

Related ports

767phonebook774acmaint-dbd777multiling-http800mdbs-daemon

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