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Port 22004 (optohost004)

IANA assigns port 22004 to optohost004: Opto Host Port 4.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
optohost004 TCP Opto Host Port 4 Doug Leany -
optohost004 UDP Opto Host Port 4 Doug Leany -

Registry dates for this port: registered 2006-09.

Check what is listening on port 22004

Linux: is anything listening on TCP 22004?
sudo ss -tlnp 'sport = :22004'
Linux: UDP 22004
sudo ss -ulnp 'sport = :22004'
Linux / macOS: which process owns the port
sudo lsof -nP -i :22004
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':22004 '
Windows (Command Prompt)
netstat -ano | findstr :22004
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 22004 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 22004
From Windows
Test-NetConnection HOST -Port 22004
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 22004

Block port 22004 in the firewall

ufw
sudo ufw deny 22004/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 22004 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 22004 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 22004' -Direction Inbound -Protocol TCP -LocalPort 22004 -Action Block
ufw
sudo ufw deny 22004/udp
iptables
sudo iptables -A INPUT -p udp --dport 22004 -j DROP
nftables
sudo nft add rule inet filter input udp dport 22004 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 22004' -Direction Inbound -Protocol UDP -LocalPort 22004 -Action Block

Related ports

22005optohost00422002optohost00222003optohost00322125dcap

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