A protocol is an agreement on how to interpret data and how to respond to messages. They generally specify message formats and legal messages. Examples of protocols include:
A port is part of socket end point in TCP and UDP. They allow the operating system to distinguish which TCP or UDP service on the host should receive incoming messages.
The confusion generally arises because, a number of ports are reserved (eg. port 80) and are generally listened to by severs expecting a particular protocol (HTTP in the case of port 80). While messages send to port 80 are generally expected to be HTTP messages, there is nothing stopping an non-HTTP server from listening on port 80 or an HTTP server from listening on an alternative port (for example 8080 or 8088).
