Port 646
ldp · TCP/UDP
| Range | System/well-known port (0–1023) |
|---|---|
| Protocol | TCP/UDP |
| Service | ldp |
Frequently asked questions
What is port 646 used for?
Port 646 is registered with the IANA for ldp (TCP/UDP). Description: LDP.
Is port 646 a well-known port?
Yes. Port 646 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 646 is open?
Locally on Linux with ss -tulpn | grep ':646\b', on Windows with netstat -ano | findstr :646. To test a remote host use Test-NetConnection <host> -Port 646 in PowerShell or nc -zv <host> 646 on Linux/macOS.
How do I open port 646 in the firewall?
Ubuntu/Debian (ufw): sudo ufw allow 646/tcp. Fedora/RHEL (firewalld): sudo firewall-cmd --add-port=646/tcp --permanent, then firewall-cmd --reload. Windows (PowerShell as administrator): New-NetFirewallRule -DisplayName "Port 646" -Direction Inbound -Protocol TCP -LocalPort 646 -Action Allow.
IANA registry entries
| Protocol | Service | Description (IANA) |
|---|---|---|
| TCP | ldp | LDP |
| UDP | ldp | LDP |