How to visually understand the "protocol" (potocal)

Potocal

N. Agreement; protocol; etiquette; Diplomatic etiquette

In the field of computer network, the word potocal is usually translated as "protocol": IP Protocol, TCP Protocol, HTTP protocol (too many omit 1000 words) ~

It refers to the agreement between the two parties on how to exchange information

Personally, if you use the meaning of "etiquette" to understand potocal, sometimes it will be more convenient.

Because examples of life can be handy, analogy, to help vivid image of understanding and memory.

For example, there is a common potocal:

A: [Look ~]

B: What do you look at?

A: What's your place?

———— three handshake, enter the fist time ————

How to visually understand the "protocol" (potocal)