Port Checker
Check whether a port on an IP address or domain is open or closed.
Common Ports
What is a Port?
Ports are logical gateways that provide access to specific services over a network. They are numbered from 0 to 65535.
TCP vs UDP
TCP is connection-based and reliable; UDP is faster but connectionless. Port checking is much more accurate with TCP.
Common Ports
Ports like 22 (SSH), 80 (HTTP), 443 (HTTPS), 3306 (MySQL), 5432 (PostgreSQL) are the most frequently used service ports.
What is a port check?
A port is a numbered entry point used to reach a specific service on a server: web servers use ports 80 and 443, SSH uses 22 and MySQL uses 3306. A port check shows whether a port on an IP address or domain can be reached from the internet.
The check is made from our server. For TCP, it tests whether a connection can be opened; for UDP, a matching request is sent to well-known services such as DNS, NTP and SNMP, and the port counts as open if an answer comes back. The result shows the port status and the response time.
How to use
- 1Enter an IP address or a domain.
- 2Enter a port number or pick one of the common ports; switch the protocol (TCP or UDP) if needed.
- 3Press Check.
Frequently asked questions
The port shows as closed but my service is running. Why?
The most common reason is a firewall: the server's own firewall (iptables, Windows Firewall), the hosting company's network firewall or your modem may be blocking the connection. A service listening only on a local address such as 127.0.0.1 cannot be reached from outside either.
How do I open a port for a device at home?
Set up port forwarding in your modem's interface to send the port to the device on your local network. Some providers use CGNAT, so you may not have a public IP address; in that case port forwarding will not work and you need to ask your provider for a public IP.
Why is the UDP check not always conclusive?
UDP is a connectionless protocol; even if a port is open, the service may not answer a request it does not understand. That is why UDP ports that do not answer are shown as closed. Results are more reliable for well-known services that answer, such as DNS, NTP and SNMP.
Can I check addresses in my local network?
No. The check is made from our server over the internet, so it cannot reach local network addresses such as 192.168.x.x. This tool can only test addresses reachable from the internet.
Which ports are used most often?
21 (FTP), 22 (SSH), 25 and 587 (SMTP), 53 (DNS), 80 (HTTP), 443 (HTTPS), 3306 (MySQL), 3389 (Remote Desktop) and 8080 (alternative HTTP) are the most commonly checked ports. Keeping unused ports closed reduces your attack surface.