Port 551
cybercash · TCP/UDP
| Range | System/well-known port (0–1023) |
|---|---|
| Protocol | TCP/UDP |
| Service | cybercash |
| Reference | RFC 1898 |
Frequently asked questions
What is port 551 used for?
Port 551 is registered with the IANA for cybercash (TCP/UDP). Description: cybercash.
Is port 551 a well-known port?
Yes. Port 551 is in the range 0–1023 (system or well-known ports). On Linux and macOS only privileged processes may bind to these ports.
How do I check whether port 551 is open?
Locally on Linux with ss -tulpn | grep ':551\b', on Windows with netstat -ano | findstr :551. To test a remote host use Test-NetConnection <host> -Port 551 in PowerShell or nc -zv <host> 551 on Linux/macOS.
How do I open port 551 in the firewall?
Ubuntu/Debian (ufw): sudo ufw allow 551/tcp. Fedora/RHEL (firewalld): sudo firewall-cmd --add-port=551/tcp --permanent, then firewall-cmd --reload. Windows (PowerShell as administrator): New-NetFirewallRule -DisplayName "Port 551" -Direction Inbound -Protocol TCP -LocalPort 551 -Action Allow.
IANA registry entries
| Protocol | Service | Description (IANA) |
|---|---|---|
| TCP | cybercash | cybercash |
| UDP | cybercash | cybercash |