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Port 3374 (cluster-disc)

IANA assigns port 3374 to cluster-disc: Cluster Disc.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
cluster-disc TCP Cluster Disc Jeff Hughes -
cluster-disc UDP Cluster Disc Jeff Hughes -

Check what is listening on port 3374

Linux: is anything listening on TCP 3374?
sudo ss -tlnp 'sport = :3374'
Linux: UDP 3374
sudo ss -ulnp 'sport = :3374'
Linux / macOS: which process owns the port
sudo lsof -nP -i :3374
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':3374 '
Windows (Command Prompt)
netstat -ano | findstr :3374
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 3374 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 3374
From Windows
Test-NetConnection HOST -Port 3374
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 3374

Block port 3374 in the firewall

ufw
sudo ufw deny 3374/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 3374 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 3374 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 3374' -Direction Inbound -Protocol TCP -LocalPort 3374 -Action Block
ufw
sudo ufw deny 3374/udp
iptables
sudo iptables -A INPUT -p udp --dport 3374 -j DROP
nftables
sudo nft add rule inet filter input udp dport 3374 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 3374' -Direction Inbound -Protocol UDP -LocalPort 3374 -Action Block

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