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Port 51820: WireGuard

Port 51820 (UDP) is used by WireGuard. This port is meant to be reachable publicly on servers that offer the service.

Updated

Port51820
ProtocolUDP
ServiceWireGuard
Internet exposureUsually open to the internet

Port 51820 is UDP-only, so the TCP-based Port Checker can’t test it. Use the local commands below.

What is port 51820 used for?

WireGuard VPN’s default port.

Should port 51820 be open?

Usually open to the internet. This port is meant to be reachable publicly on servers that offer the service. WireGuard doesn’t answer unauthenticated packets, so it can look filtered to scanners even when it works.

See what is listening on port 51820

# Linux
sudo ss -ulnp | grep ':51820 '

# macOS
sudo lsof -nP -i UDP:51820

# Windows (PowerShell)
Get-NetUDPEndpoint -LocalPort 51820

Open or block port 51820 in a firewall

# Ubuntu / Debian (ufw)
sudo ufw allow 51820/udp
sudo ufw deny 51820/udp

# Windows (PowerShell, as administrator)
New-NetFirewallRule -DisplayName "Port 51820" -Direction Inbound -Protocol UDP -LocalPort 51820 -Action Allow

On cloud servers, also open the port in the provider’s security group or network firewall. At home, a service behind a router needs a port-forwarding rule to the device’s local IP.

Port CheckerTest whether a server accepts connections on specific ports — web (80/443), mail (25/587/993), SSH, databases or remote desktop — and see which are open, closed or filtered by a firewall.
Open the tool

Frequently asked questions

What is port 51820?
WireGuard VPN’s default port.
Is it safe to open port 51820?
Usually open to the internet. This port is meant to be reachable publicly on servers that offer the service.
How do I check if port 51820 is open?
Port 51820 uses UDP, which a TCP check can’t test. On the server, run ss -ulnp (Linux) or Get-NetUDPEndpoint (Windows) to see if something listens.