Core Protocol
Communication between server and clients is done by exchanging packets over a network channel. The client establishes the connection, sending the first packet. The server answers by sending back a packet stating the acceptance or refusal of the connection, or with a request for a further authentication. If the connection is accepted, the acceptance packet contains data for the client to use in the subsequent interaction with the server.
After connection is established, the client and the server exchange four different types of packets over the channel:
- Request: the client requests information from the server or requests it to perform an action.
- Reply: the server responds to a request. Not all requests generate replies.
- Event: the server sends an event to the client, e.g., keyboard or mouse input, or a window being moved, resized or exposed.
- Error: the server sends an error packet if a request is invalid. Since requests are queued, error packets generated by a request may not be sent immediately.
The X server provides a set of basic services. The client programs realize more complex functionalities by interacting with the server.
Read more about this topic: X Window System Protocols And Architecture
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