Port 121

erpc · TCP/UDP

RangeSystem/well-known port (0–1023)
ProtocolTCP/UDP
Serviceerpc

Frequently asked questions

What is port 121 used for?

Port 121 is registered with the IANA for erpc (TCP/UDP). Description: Encore Expedited Remote Pro.Call.

Is port 121 a well-known port?

Yes. Port 121 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 121 is open?

Locally on Linux with ss -tulpn | grep ':121\b', on Windows with netstat -ano | findstr :121. To test a remote host use Test-NetConnection <host> -Port 121 in PowerShell or nc -zv <host> 121 on Linux/macOS.

How do I open port 121 in the firewall?

Ubuntu/Debian (ufw): sudo ufw allow 121/tcp. Fedora/RHEL (firewalld): sudo firewall-cmd --add-port=121/tcp --permanent, then firewall-cmd --reload. Windows (PowerShell as administrator): New-NetFirewallRule -DisplayName "Port 121" -Direction Inbound -Protocol TCP -LocalPort 121 -Action Allow.

IANA registry entries

ProtocolServiceDescription (IANA)
TCPerpcEncore Expedited Remote Pro.Call
UDPerpcEncore Expedited Remote Pro.Call

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