What is Port Number?

The port number is nothing but what port you having a machine.
Example: In my PC, I have a USB port, VGA port, Parallel ports, Headset port, etc.. whatever it is we need to know where exactly plug to our USB and Where exactly plug to our Pendrive we don’t know means we can’t able to use it. In my PC my SQL is running, oracle is running, TCP is running etc…this many technologies are running in my one single PC I writing a java code or python code to connect with my SQL it is confused to connect SQL it doesn’t know it get confused because these many technologies(SQL, Oracle, TCP) are running in same IP address so we have to provide port number it will search for what process having this port number once its find out my SQL is configuration with that port number than its easily connected.