Many applications, especially those involving networking, rely on the ability to open specific ports so that other computers or devices can connect to them. In a Unix-like operating system, there are several ways to check if a port is open, each with its strengths and weaknesses. One way to check if a port is open is to use the netstat command. The netstat command provides information about the network connections on your system, including which ports are open and which programs are using them.
The netstat command can be used with a variety of options to customize the output. For example, the -a option will show all open ports, the -n option will show numerical addresses instead of hostnames, and the -p option will show the programs that are using each port. Here is an example of how to use the netstat command to check if port 80 is open: