Application-layer protocols (cont).
API: application programming interface
defines interface between application and transport layer
socket: Internet API
- two processes communicate by sending data into socket, reading data out of socket
Q: how does a process “identify” the other process with which it wants to communicate?
- IP address of host running other process
- “port number” - allows receiving host to determine to which local process the message should be delivered
… lots more on this later.