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Port 3121 (pcmk-remote)

IANA assigns port 3121 to pcmk-remote: The pacemaker remote (pcmk-remote) service extends high availability functionality outside of the Linux cluster into remote nodes..

Registered (user) port, 1024-49151 TCP

IANA assignment

Service nameProtoDescriptionAssigneeReference
pcmk-remote TCP The pacemaker remote (pcmk-remote) service extends high availability functionality outside of the Linux cluster into remote nodes.
port 3121 previously noted "Removed on 2003-09-17" David Vossel -

Registry dates for this port: last modified 2013-03-15.

Check what is listening on port 3121

Linux: is anything listening on TCP 3121?
sudo ss -tlnp 'sport = :3121'
Linux / macOS: which process owns the port
sudo lsof -nP -i :3121
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':3121 '
Windows (Command Prompt)
netstat -ano | findstr :3121
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 3121 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 3121
From Windows
Test-NetConnection HOST -Port 3121

Block port 3121 in the firewall

ufw
sudo ufw deny 3121/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 3121 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 3121 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 3121' -Direction Inbound -Protocol TCP -LocalPort 3121 -Action Block

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