Port 5550 (cbus)

IANA assigns port 5550 to cbus: Model Railway control using the CBUS message protocol.

Registered (user) port, 1024-49151 TCP

IANA assignment

Service nameProtoDescriptionAssigneeReference

cbus TCP Model Railway control using the CBUS message protocol MERG -

Registry dates for this port: registered 2017-01-03.

Linux: is anything listening on TCP 5550?

sudo ss -tlnp 'sport = :5550'

Linux / macOS: which process owns the port

sudo lsof -nP -i :5550

Older Linux / BSD (net-tools)

sudo netstat -tlnp | grep ':5550 '

Windows (Command Prompt)

netstat -ano | findstr :5550

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 5550 -State Listen | Select LocalAddress,OwningProcess

From another machine

nc -vz -w 5 HOST 5550

From Windows

Test-NetConnection HOST -Port 5550

ufw

sudo ufw deny 5550/tcp

iptables

sudo iptables -A INPUT -p tcp --dport 5550 -j DROP

nftables

sudo nft add rule inet filter input tcp dport 5550 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block TCP 5550' -Direction Inbound -Protocol TCP -LocalPort 5550 -Action Block

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