Port Checker – check open ports online

Enter the public IP address or hostname, select a protocol, game or custom ports, and click “Check ports”. Our server makes a real TCP connection or sends a UDP probe to each selected port. To check whether port 443 is open, for example, use the “HTTP + HTTPS” preset (ports 80 and 443). The same result is cached for up to 20 seconds, so wait briefly after changing your firewall or router before checking again.

“Open”: The connection was accepted; a service is running on the port. “Closed”: The server actively refused the connection; no program is currently listening on the port. “No response (possibly firewall)”: No response arrived within 2.5 seconds, usually because a firewall silently dropped the request.

Yes. In “Custom ports” mode, select TCP or UDP and mark individual ports with /udp or /tcp+udp. Presets such as DNS or TeamSpeak already include UDP ports. Unlike TCP, UDP has no handshake: An open UDP port often does not respond to an empty test request and looks the same from outside as a port blocked by a firewall. The tool therefore shows “Open or filtered”. Only an explicit refusal produces “Closed”.

First, find your public IP address, for example with our “What is my IP address?” tool. Then start the service you forwarded the port for and check the port here using your public IP. Because the check comes from the internet, you can see whether your router and firewall really allow traffic through. If your connection shares a public IPv4 address with other customers (CGNAT, DS-Lite), IPv4 port forwarding is often not possible.

In “Custom ports” mode, you can check up to 5 ports at a time, including a small range such as 27015-27019. Protocol and game presets may contain more ports: the “Mail” preset, for example, has 7, but the maximum is 15 per check. There is a short wait of about 8 seconds between checks. These limits are intentional: they prevent this free tool from being misused as a port scanner against other people's servers. Check larger lists in several batches.

No. Private, internal and local address ranges (such as 192.168.x.x, 10.x.x.x or localhost) are blocked for security reasons, even if a hostname points to one of these addresses. The tool only checks publicly reachable servers. To see which ports are listening on your own computer, use local commands such as netstat -ano on Windows or ss -tulpn on Linux.

In “Game” mode, select one of the games ZAP-Hosting offers as a Game Server. The tool then checks that game's configured default ports using the appropriate protocol, such as its game and query ports, so you don't have to look them up individually.

Port Checker only tests network-level reachability. The actual connection can still fail if no suitable service is running, the application is misconfigured or a firewall within the server specifically blocks your protocol.