How to determine whether a port is open in Linux

The methods for Linux to determine whether a port is open include netstat command, ss command, lsof command and telnet command. Detailed introduction: 1. Use the netstat command. netstat is a command line tool used to view network connections and port status. You can use the netstat command to view the port status on the current system; 2. Use the ss command. ss is a command line tool used to view the status of the network connection and port. A command line tool for network connection and socket status that provides more detailed and faster information than netstat and more.

The operating system of this tutorial: linux6.4.3 system, DELL G3 computer.

In Linux, there are many ways to determine the status of a port. The following are some commonly used methods:

1. Use the netstat command: netstat is a command line tool used to view network connections and port status. You can use the netstat command to view the port status on the current system. For example, to view the status of port 80, you can execute the following command:

   netstat -an | grep :80

If port 80 is in the listening state, relevant information will be displayed. If port 80 is not open, no output will be displayed.

2. Use the ss command: ss is a command line tool used to view network connections and socket status. It provides more detailed and faster information than netstat. You can use the ss command to view the status of the port. For example, to view the status of port 80, you can execute the following command:

   ss -ltn | grep :80

If port 80 is in the listening state, relevant information will be displayed. If port 80 is not open, no output will be displayed.

3. Use the lsof command: lsof is a command line tool used to view open files and processes on the system. It can also be used to view the status of a port. For example, to view the status of port 80, you can execute the following command:

   lsof -i :80

If port 80 is open, relevant information will be displayed. If port 80 is not open, no output will be displayed.

4. Use the telnet command: Telnet is a command line tool used for remote login and testing network connections. You can use the telnet command to try to connect to a specified port. For example, to test whether port 80 with the host's IP address 192.168.0.1 is open, you can execute the following command:

   telnet 192.168.0.1 80

If port 80 is open, the connection will be successful. If port 80 is not open, the connection will fail.

These methods are just some common methods for determining port status in Linux. Depending on your specific needs and network environment, additional tools or options may be required. If you need more detailed information, it is recommended to consult the Linux man manual or refer to relevant documents.

In summary, there are many ways to determine whether a port is open in Linux, including using the netstat command, ss command, lsof command and telnet command. These tools can help you quickly view the status of your ports for network debugging and troubleshooting.

The above is the detailed content of How to determine whether a port is open in Linux. For more information, please follow other related articles on the PHP Chinese website!