Computer science from A to Z
P is for Protocol
“Hello? - Hi, it's Michael. Can I come over? - Yes, sure. - See you soon. - Bye .” This may be a banal conversation, but it follows well established practices: a protocol.
In order to understand each other, computers too follow protocols.
When an e-mail relay transmits a message to another relay it follows a standardised procedure. The transmitter identifies itself, then transmits the sender's address, the recipient's address and the content of the message, and finally signals the end of the transmission. At each stage, the receiver responds “OK ” or “Error ” to guarantee the reliability of the communication.
Every application uses specially adapted protocols: HTTP for the web, HTTPS for secure transactions, WAP for connection of mobile phones to the Internet...
Wireless networks or contactless badge readers require special protocols: it is necessary to identify the interlocutor with whom you want to communicate, out of all those emitting signals at the same time in the surrounding area.
Thus, the art of conversation by computer is constantly being refined...