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Port 12109 (rets-ssl)

IANA assigns port 12109 to rets-ssl: RETS over SSL.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
rets-ssl TCP RETS over SSL Jeremy Crawford -
rets-ssl UDP RETS over SSL Jeremy Crawford -

Registry dates for this port: registered 2003-02.

Check what is listening on port 12109

Linux: is anything listening on TCP 12109?
sudo ss -tlnp 'sport = :12109'
Linux: UDP 12109
sudo ss -ulnp 'sport = :12109'
Linux / macOS: which process owns the port
sudo lsof -nP -i :12109
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':12109 '
Windows (Command Prompt)
netstat -ano | findstr :12109
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 12109 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 12109
From Windows
Test-NetConnection HOST -Port 12109
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 12109

Block port 12109 in the firewall

ufw
sudo ufw deny 12109/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 12109 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 12109 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 12109' -Direction Inbound -Protocol TCP -LocalPort 12109 -Action Block
ufw
sudo ufw deny 12109/udp
iptables
sudo iptables -A INPUT -p udp --dport 12109 -j DROP
nftables
sudo nft add rule inet filter input udp dport 12109 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 12109' -Direction Inbound -Protocol UDP -LocalPort 12109 -Action Block

Related ports

12012vipera12013vipera-ssl12121nupaper-ss12168cawas

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