端口检测
我们从服务器向你访问本页所用地址上的指定端口发起一次 TCP 连接——绝不连接其他地址。
你的公网地址: 216.73.217.58
为避免变成扫描服务，本工具只检测你的请求来源地址。要检测其他网络，请在该网络中打开本页。
这种方式只能检测 TCP。UDP 服务（WireGuard、许多游戏）不会回应未经请求的探测，因此无法区分开放和关闭的 UDP 端口。
此内容尚无中文（中国）版本。在发布译文之前以英语显示。
A port is the number that tells a device which program a connection is for: 443 for a web server, 22 for SSH, 25565 for a Minecraft server. When you run something at home that others should reach — a game server, a security camera, a NAS, a remote desktop — your router has to forward the port from its public address to the device inside your network.
This tool answers one question: is that port reachable from the internet right now? Our server opens a single TCP connection to the port you choose on the address your request comes from and reports what happens:
- Open — something completed the TCP handshake. The service is reachable.
- Closed — your connection answered with a refusal (RST): the router or the device is there, but nothing listens on that port, or the forward points to the wrong device.
- No answer (filtered) — nothing came back within three seconds. A firewall drops the packets, the router does not forward the port, or you are behind carrier-grade NAT (CGNAT): many customers share one public IPv4 address, so incoming connections cannot be forwarded to you at all. Mobile connections are almost always behind CGNAT, and some fixed-line providers use it too.
The tool never tests another address: a port checker that accepts any target is a scanner for other people’s networks. Only TCP can be tested; UDP services do not answer an unsolicited probe.
常见问题
My port shows as filtered although I forwarded it. Why?
Check three things: the router's WAN address must be the same as the address shown here (otherwise you are behind CGNAT), the forward must point to the device's current local address, and the device's own firewall must allow the port. Some providers also block common server ports such as 25 and 80 on home lines.
How do I know whether I am behind CGNAT?
Open your router's status page. If its internet (WAN) address differs from your public address here, or starts with 100.64–100.127, you share a public address with others. Ask your provider for a public IPv4 address (often a paid static IP) or use IPv6, where every device can be reachable.
Is an open port dangerous?
Only if what listens on it is outdated or badly protected. Expose only what you need, keep it updated, use strong passwords or keys, and close forwards you no longer use.
Can I test my server's ports from here?
Only from the server's own connection: the tool tests the address the page is loaded from. To test a remote server, open this page on that network, or use a tool you run yourself.