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Port 678 (ggf-ncp)

IANA assigns port 678 to ggf-ncp: GNU Generation Foundation NCP.

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

IANA assignment

Service nameProtoDescriptionAssigneeReference
ggf-ncp TCP GNU Generation Foundation NCP Noah Paul -
ggf-ncp UDP GNU Generation Foundation NCP Noah Paul -

Check what is listening on port 678

Linux: is anything listening on TCP 678?
sudo ss -tlnp 'sport = :678'
Linux: UDP 678
sudo ss -ulnp 'sport = :678'
Linux / macOS: which process owns the port
sudo lsof -nP -i :678
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':678 '
Windows (Command Prompt)
netstat -ano | findstr :678
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 678 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 678
From Windows
Test-NetConnection HOST -Port 678
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 678

Block port 678 in the firewall

ufw
sudo ufw deny 678/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 678 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 678 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 678' -Direction Inbound -Protocol TCP -LocalPort 678 -Action Block
ufw
sudo ufw deny 678/udp
iptables
sudo iptables -A INPUT -p udp --dport 678 -j DROP
nftables
sudo nft add rule inet filter input udp dport 678 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 678' -Direction Inbound -Protocol UDP -LocalPort 678 -Action Block

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Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.