[clarry]

> In all cases, one node must send the first packet. The node sending the packet is the client, and the destination of the packet is the server.

I'm pretty sure you are just making up new definitions. It's kinda like saying that whoever says the first word in class is the teacher and the rest are student.

The fact is that both peers send packets and the first packet isn't particularly significant, except from a stateful connection or firewall perspective.

[chatmasta]

Well, let’s breakout Wikipedia [0]

> Clients therefore initiate communication sessions with servers which await incoming requests.

> Both client-server and master-slave are regarded as sub-categories of distributed peer-to-peer systems.

[0] https://en.m.wikipedia.org/wiki/Client–server_model

[clarry]

> Clients therefore initiate communication sessions with servers which await incoming requests.

Dogs walk on four feet, therefore anything that walks on four feet is a dog?

> Both client-server and master-slave are regarded as sub-categories of distributed peer-to-peer systems.

Dogs are canids, that doesn't mean all canids are dogs.

The client-server model really entails more than having one party that sends a packet before the other. Some illuminating details and a shallow comparison to the peer-to-peer architecture can be found in the article you linked.