PortChecker.us is a free online tool to find open ports in your system. This tool lets you scan open ports which may prove security holes to hackers. You can also test whether port forwarding is working or not.

FTP - 20 SSH - 22 SMTP - 25 HTTP - 80 IMAP - 993 RDP - 3389 POP3 - 110 Quick Scan[15 Port] Long Scan[36 Port]

    What is open port checker?

    This tool is useful for checking port in your router is open or close. This is online security tool check port open or being blocked in your firewall system.

    What are ports?

    Ports are virtual pathways on which information on the Internet travel. There are 65,536 ports to choose from. A good analogy is to think of ports like extensions on a phone sytstem.

    Ports 0 to 1023 - Well known port numbers. Only special companies like: MS SQL services (1433), Mail services POP3(110), IMAP(143), SMTP(25), Web services HTML(80).

    Ports 1024 to 49151 - Registered ports; meaning they can be registered to specific protocols by software corporations.

    Ports 49152 to 65536 - Dynamic or private ports; meaning that they can be used by just about anybody.

    What is Port Forwarding?

    Port Forwarding is a special function on the router, allowing transfer of data packets from the outside (from the Internet) to devices or computers on your local network (LAN). Usually the port on your router will be closed to prevent hackers on your system. But when you use the service to connect through port on the router you need to open it. For example: Yahoo! Messenger you need one of the following ports must be open: 5061, 443, 80.



    Common ports

    FTP Control 21
    SSH 22
    Telnet 23
    SMTP 25
    DNS 53
    HTTP / Web 80
    POP3 110
    IMAP 143
    HTTPS 443
    IMAP SSL 993
    POP3 SSL 995
    MSSQL 1433
    REMOTE 3389
    VNC 5900