Port 391
synotics-relay · TCP/UDP
| Range | System/well-known port (0–1023) |
|---|---|
| Protocol | TCP/UDP |
| Service | synotics-relay |
Frequently asked questions
What is port 391 used for?
Port 391 is registered with the IANA for synotics-relay (TCP/UDP). Description: SynOptics SNMP Relay Port.
Is port 391 a well-known port?
Yes. Port 391 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 391 is open?
Locally on Linux with ss -tulpn | grep ':391\b', on Windows with netstat -ano | findstr :391. To test a remote host use Test-NetConnection <host> -Port 391 in PowerShell or nc -zv <host> 391 on Linux/macOS.
How do I open port 391 in the firewall?
Ubuntu/Debian (ufw): sudo ufw allow 391/tcp. Fedora/RHEL (firewalld): sudo firewall-cmd --add-port=391/tcp --permanent, then firewall-cmd --reload. Windows (PowerShell as administrator): New-NetFirewallRule -DisplayName "Port 391" -Direction Inbound -Protocol TCP -LocalPort 391 -Action Allow.
IANA registry entries
| Protocol | Service | Description (IANA) |
|---|---|---|
| TCP | synotics-relay | SynOptics SNMP Relay Port |
| UDP | synotics-relay | SynOptics SNMP Relay Port |