Port Number view command

During Tomcat startup, exceptions may occur, such as the absence of JRE and occupation of the port number. How can I check whether the port number is occupied? A fport.exe tool is available in the old instructor's lecture to conveniently check the port usage. However, if you cannot use this tool, you need to know the CMD command and use it to check the port usage, the following figure shows the search information. You can view the port in the CMD window,

To view the port in Windows 2000/XP/Server 2003, run the netstat command:

Click Start> Run, type cmd, and press enter to open the Command Prompt window. Type "netstat-a-n" in the command prompt. Press the Enter key to view the TCP and UDP connection port numbers and statuses displayed in numbers.

TIPS: netstat command usage
Command Format: netstat-a-e-n-o-s-

-A indicates that all active TCP connections and TCP and UDP ports listened by the computer are displayed.

-E indicates the number of bytes sent and received over the Ethernet, and the number of packets.

-N indicates that only the active TCP connection addresses and port numbers are displayed in numbers.

-O indicates that active TCP connections are displayed and the process ID (PID) of each connection is included ).

-S indicates that statistics of various connections are displayed by protocol, including the port number.

-An: view all open ports
Close/enable port
Before introducing the functions of various ports, we will first introduce how to disable/enable ports in windows, because the default situation is, many insecure or useless ports are enabled, for example, port 23 of the Telnet service, port 21 of the FTP service, port 25 of the SMTP service, and port 135 of the RPC service. To ensure system security, we can disable/enable the port through the following methods.

Close the port
For example, to disable port 25 of the SMTP service in Windows 2000/XP, you can do this: first open "Control Panel", double-click "Administrative Tools", and then double-click "service ". In the displayed service window, find and double-click the "Simple Mail Transfer Protocol (SMTP)" service and click "stop" to stop the service, select "disabled" in "Start type" and click "OK. In this way, closing the SMTP service is equivalent to closing the corresponding port.

Enable Port
If you want to enable this port, you only need to select "Auto" in "Start type", click "OK", and then open the service, in "service status", click "start" to enable the port. Finally, click "OK.

Tip: the "service" option is not available in Windows 98. You can use the firewall rule setting function to disable/enable the port.