The Protocol is a set of formal rules and conventions that govern how data is transmitted and received between two or more communicating devices. It ensures that communication is orderly, efficient, and reliable. A protocol defines many aspects of communication, including syntax (the structure and format of the data), semantics (the meaning of the data), and timing (when and how fast data is sent). It's like a diplomatic protocol for machines; both sides must follow the same rules to understand each other and avoid chaos. In networking and instrument control, numerous protocols operate at different levels.
At a low level, a serial communication protocol like RS-232C defines the voltage levels for bits, the baud rate, and the use of start and stop bits. At a higher level, network protocols like IP (Internet Protocol) define how to address and route packets across a network, while TCP (Transmission Control Protocol) defines how to ensure that all those packets arrive correctly and in order. On top of these, an application-level protocol like SCPI (Standard Commands for Programmable Instruments) defines the actual command strings that are used to control a device. For communication to be successful, all devices involved must support and be correctly configured to use the same set of protocols.
IP: Internet Protocol, RFC 791
TCP: Transmission Control Protocol, RFC 793
UDP: User Datagram Protocol, RFC768
HTTP: Hyper Text Transfer Protocol, RFC7231
The Internet Engineering Task Force (IETF) Official website (https://www.ietf.org/)