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Port 22003 (optohost003)

IANA assigns port 22003 to optohost003: Opto Host Port 3.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
optohost003 TCP Opto Host Port 3 Doug Leany -
optohost003 UDP Opto Host Port 3 Doug Leany -

Registry dates for this port: registered 2006-09.

Check what is listening on port 22003

Linux: is anything listening on TCP 22003?
sudo ss -tlnp 'sport = :22003'
Linux: UDP 22003
sudo ss -ulnp 'sport = :22003'
Linux / macOS: which process owns the port
sudo lsof -nP -i :22003
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':22003 '
Windows (Command Prompt)
netstat -ano | findstr :22003
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 22003 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 22003
From Windows
Test-NetConnection HOST -Port 22003
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 22003

Block port 22003 in the firewall

ufw
sudo ufw deny 22003/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 22003 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 22003 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 22003' -Direction Inbound -Protocol TCP -LocalPort 22003 -Action Block
ufw
sudo ufw deny 22003/udp
iptables
sudo iptables -A INPUT -p udp --dport 22003 -j DROP
nftables
sudo nft add rule inet filter input udp dport 22003 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 22003' -Direction Inbound -Protocol UDP -LocalPort 22003 -Action Block

Related ports

22001optocontrol22002optohost00222004optohost00422005optohost004

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