The following describes the common server ports. For more information on service application ports for Windows, see the official Microsoft document (Windows Service Overview and Network Port Requirements).
|21||FTP||An open FTP server port for uploading and downloading.|
|22||SSH||Port 22 is the SSH port. It is used to remotely connect to Linux servers in CLI mode.|
|25||SMTP||SMTP server's open port for sending emails.|
|80||HTTP||This port is used for web services such as IIS, Apache, and Nginx to provide external access.|
|110||POP3||Port 110 is open for the POP3 (email protocol 3) service.|
|137, 138, 139||NetBIOS protocol||Ports 137 and 138 are UDP ports for transferring files through My Network Places.
Port 139: connections over port 139 attempt to access the NetBIOS/SMB service. This protocol is used for file and printer sharing on Windows and SAMBA.
|143||IMAP||Port 143 is mainly used for Internet Message Access Protocol (IMAP) v2, a protocol for receiving emails that is similar to POP3.|
|443||HTTPS||A web browsing port. HTTPS is another type of HTTP that provides encryption and transmission through secure ports.|
|1433||SQL Server||Port 1433 is the default port for SQL Server. SQL Server uses two ports: port 1433 for TCP and port 1434 for UDP. Port 1433 is used for SQL Server to provide external services, whereas port 1434 is used to respond to the requester regarding which TCP/IP port is being used by SQL Server.|
|3306||MySQL||Port 3306 is the default port for MySQL databases and is used to provide external services.|
|3389||Windows Server Remote Desktop Services||Port 3389 is the port for remote desktop service on Windows 2000/2003 Server, through which you can connect to a remote server by using the Remote Desktop connection tool.|
|8080||Proxy port||Similar to port 80, port 8080 is used for the WWW proxy service for web browsing. The port number extension ":8080" is often appended to the URL when users visit a website or use a proxy server. In addition, after the Apache Tomcat web server is installed, the default service port is port 8080.|