acknowledgement: When the receiving computer sends a notification back to the source computer indicating that data has been received.
buffering: Temporarily holding on to data that has been sent or received until the computer is sure the data is no longer needed.
listen: When a server application is started and ready to accept incoming connections from client applications.
port: A way to allow many different server applications to be waiting for incoming connections on a single computer. Each application listens on a different port. Client applications make connections to well-known port numbers to make sure they are talking to the correct server application.