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Port 684 (corba-iiop-ssl)

IANA assigns port 684 to corba-iiop-ssl: CORBA IIOP SSL.

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

IANA assignment

Service nameProtoDescriptionAssigneeReference
corba-iiop-ssl TCP CORBA IIOP SSL Andrew Watson -
corba-iiop-ssl UDP CORBA IIOP SSL Andrew Watson -

Check what is listening on port 684

Linux: is anything listening on TCP 684?
sudo ss -tlnp 'sport = :684'
Linux: UDP 684
sudo ss -ulnp 'sport = :684'
Linux / macOS: which process owns the port
sudo lsof -nP -i :684
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':684 '
Windows (Command Prompt)
netstat -ano | findstr :684
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 684 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 684
From Windows
Test-NetConnection HOST -Port 684
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 684

Block port 684 in the firewall

ufw
sudo ufw deny 684/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 684 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 684 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 684' -Direction Inbound -Protocol TCP -LocalPort 684 -Action Block
ufw
sudo ufw deny 684/udp
iptables
sudo iptables -A INPUT -p udp --dport 684 -j DROP
nftables
sudo nft add rule inet filter input udp dport 684 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 684' -Direction Inbound -Protocol UDP -LocalPort 684 -Action Block

Related ports

682xfr683corba-iiop685mdc-portmapper686hcp-wismar

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