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Quickly check the open port status of an IP or domain for network diagnostics and security validation.
Port checking is used to verify whether a specific service is running and accessible on a server. It attempts to establish a TCP connection with the target port. If the connection is successful, the port is considered "open", and we can measure the "TCP Ping" latency (the time required to complete the connection handshake). If the connection fails or times out, the port is "closed" or filtered by a firewall.
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When a website is inaccessible or a service is abnormal, a port checker helps you quickly determine if the target server's network services are responding properly. This tool sends connection requests to the TCP ports of a specified IP or domain and determines the port status based on the response, returning one of three results: open, closed, or filtered. Ports are logical endpoints for application communication in computer networks, with port numbers ranging from 1 to 65535.
What does a "filtered" status mean in a port check?
It means a firewall or security device has blocked the probe request, making it impossible to determine the true status of the port.
Why does the tool primarily check TCP ports?
TCP port checking uses a mature SYN handshake mechanism, yielding reliable results. UDP checking requires sending data packets and waiting for a response, which has a lower success rate and is easily interfered with by firewalls. Therefore, this tool focuses on TCP protocol checking.
Please use this tool only within authorized scopes. Avoid high-frequency scanning of the same target to prevent being blocked. Note that results are affected by network latency and firewall policies; a filtered status simply indicates a network obstruction. UDP port checking is not supported.
For web service diagnostics, it is recommended to prioritize checking ports 80 (HTTP) and 443 (HTTPS). For remote management services, check ports 22 (SSH), 3389 (RDP), or 23 (Telnet). Typical example: Checking port 80 on baidu.com usually returns an open status, while port 22 is typically closed or filtered because it does not expose SSH services publicly.
