The TCP/IP application layer is responsible for end-user communication and application-specific data exchange over the Internet. Its primary function is to provide a platform-independent interface between software applications and the underlying network protocols.
It relies on destination ports to identify the specific application or service a data packet is intended for. Destination ports and IP addresses help route data to the correct application running on a device.
For instance, web browsers use port 80 for HTTP, while email clients use port 25 for SMTP. By associating port numbers with applications, the application layer ensures seamless and reliable communication, allowing multiple applications to operate concurrently on the same device while ensuring data reaches the correct destination.