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Port 674 (acap)

IANA assigns port 674 to acap: ACAP.

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

IANA assignment

Service nameProtoDescriptionAssigneeReference
acap TCP ACAP Chris Newman -
acap UDP ACAP Chris Newman -

Registry dates for this port: last modified 2010-10-15.

Check what is listening on port 674

Linux: is anything listening on TCP 674?
sudo ss -tlnp 'sport = :674'
Linux: UDP 674
sudo ss -ulnp 'sport = :674'
Linux / macOS: which process owns the port
sudo lsof -nP -i :674
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':674 '
Windows (Command Prompt)
netstat -ano | findstr :674
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 674 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 674
From Windows
Test-NetConnection HOST -Port 674
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 674

Block port 674 in the firewall

ufw
sudo ufw deny 674/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 674 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 674 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 674' -Direction Inbound -Protocol TCP -LocalPort 674 -Action Block
ufw
sudo ufw deny 674/udp
iptables
sudo iptables -A INPUT -p udp --dport 674 -j DROP
nftables
sudo nft add rule inet filter input udp dport 674 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 674' -Direction Inbound -Protocol UDP -LocalPort 674 -Action Block

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672vpps-qua673cimplex675dctp676vpps-via

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