In order to identify connection uniquely , port number is not sufficient , Two host chossen the same host
or IP address is also not sufficient because there is a chance that the two host have same IP addresses
, they can choose any port number inside the computer , it might so happen that , the number which they have choose is also 'X'
So we are not going to use Only prt number , Or only IP address to identify the connection uniquely
therefore we combine both (IP + Port = Socket)