Describe communications at the application level - give an example.

What will be an ideal response?

Each client and server application installed on a computer listens at a predetermined address that uniquely identifies the application on the computer. This address is a number and is called a port number, port, or port address. For example, you can address a web server by entering into a browser address box an IP address followed by a colon and then 80, which is the port number for a web server application. Suppose a computer with an IP address of 136.60.30.5 is running both an email server, which listens at port 25, and a web server application listening at port 80. If a client computer sends a request to 136.60.30.5:25, the email server that is listening at that port responds. On the other hand, if a request is sent to 136.60.30.5:80, the web server listening at port 80 responds