Connection & network
Open port checker
Check which ports on your own public IP can be reached from the internet – perfect for testing port forwarding.
What the results mean
- Open – something on your network accepted the connection. Port forwarding works, and anyone on the internet can reach this service, so make sure it is secured.
- Closed – your router or device answered "nothing is listening here". The port is reachable but no program is using it.
- Filtered – no answer at all. A firewall (often your router or your ISP) silently drops the traffic. This is the safest state for ports you do not use.
Why can't I check another IP address?
Scanning other people's devices without permission is not allowed. That's why this tool only tests the address you are visiting from.
Common ports and what uses them
| Port | Protocol | Typical use |
|---|---|---|
| 22 | TCP | SSH – remote server login |
| 80 / 443 | TCP | Web server (HTTP / HTTPS) |
| 3389 | TCP | Windows Remote Desktop |
| 25565 | TCP | Minecraft Java server |
| 8080 / 8443 | TCP | Alternative web ports, NAS and camera panels |
| 32400 | TCP | Plex Media Server |
| 51820 | UDP | WireGuard VPN |
This checker tests TCP ports by trying to open a connection. UDP services such as WireGuard do not reply to empty probes, so they cannot be reliably tested this way.
Step-by-step: getting a port to show “open”
- Start the program that should listen on the port (game server, Plex, web server). A port only shows open when something is listening.
- Allow it through the computer’s firewall. Windows Defender Firewall and macOS often block new servers until you click “Allow”.
- Give the computer a fixed local IP (a DHCP reservation on your router) so the forwarding rule does not break after a reboot.
- Create a port forwarding rule on your router: external port → the computer’s local IP and internal port.
- Check that your router’s WAN IP matches the public IP shown on our home page. If it starts with 100.64–100.127, 10., 172.16–31. or 192.168., you are behind another NAT and the port cannot be opened from your side – see What is CGNAT?
- Test here from the same network, then ask a friend outside your network to connect.
Our complete port forwarding guide covers each step in detail with screenshots of typical router menus described in words.
Security tip: every open port is a door into your network. Only open what you need, keep the software behind it updated, use strong passwords, and avoid exposing Remote Desktop (3389) or camera panels directly – a VPN such as WireGuard is a much safer way to reach them from outside.
Port checker – frequently asked questions
Why does my port show open here but my friends still can’t connect?
They may be using the wrong address (they need your public IP, not 192.168.x.x), your public IP may have changed, or the game uses an additional UDP port that this test cannot check.
Does my internet provider block ports?
Some providers block port 25 (to stop spam) and occasionally 80 or 445 on home connections. If one specific port is always filtered but others work, ask your provider or use a different external port.