From 444bfa2f41143aff7490e4fa21565947565b7d30 Mon Sep 17 00:00:00 2001 From: nasr Date: Fri, 13 Mar 2026 22:31:21 +0100 Subject: cleanup: generalisation --- xlib-tutorial/server.html | 89 ----------------------------------------------- 1 file changed, 89 deletions(-) delete mode 100644 xlib-tutorial/server.html (limited to 'xlib-tutorial/server.html') diff --git a/xlib-tutorial/server.html b/xlib-tutorial/server.html deleted file mode 100644 index a408834..0000000 --- a/xlib-tutorial/server.html +++ /dev/null @@ -1,89 +0,0 @@ - - -Xlib programming tutorial: What is all this "client-server" stuff ? - - - -

What does all this stuff about "client-server" mean ?

- -Everybody says that X has a "client-server" architecture. So this must -be true, but what does it mean ? - -

- -Well, basically a client-server architecture is conceptually a simple -thing, but the consequences may be a bit subtle, especially the way it -is implemented in the Xlib. - -

What is a client-server architecture ?

- -A client-server architecture is a general mechanism for handling a -shared resource that several programs may want to access -simultaneously. In the case of X, the shared resources are the drawing -area and the input channel. If every process was allowed to write on -it at its will, several processes may want to draw at the same place, -resulting in an unpredictable chaos. Thus, only one process is allowed -to get access to the drawing area: the X server. The processes wanting -to draw stuff or get inputs send requests to the X servers (they are -"clients"). They do this over a communication channel. The X server -performs the requests for its clients, and sends them back replies. It -may also send messages without explicit client's requests to keep them -informed of what is going on. These messages sent by the server on its -own behalf are called "events". - -

Advantages of the client-server architecture

- -The client-server architecture has several advantages, many of them -resulting from the ability to run the server and the clients on -separate machines. Here are some advantages: - -

A client-server architectured system can be very robust: since - the server runs in its own address space, it can protect itself - against poorly written clients. Thus, if a client has a bug, it - will crash alone, the server and the other clients still running - as if nothing has happened. - -
The client and the server don't have to run on the same machine, - so we have some communication mechanism here. - -
The client and the server may run on separate machines, resulting - in a better load distribution (possibly). - -
The client and the server don't have to run on the same hardware, - operating system, etc., giving a better interoperability. - -

- -

Structure of the X client-server architecture

- -As we already mentioned, the server and a client communicates over a -communication channel. This channel is composed of two layers: the -low-level one, which is responsible for carrying bytes in a reliable -way (that is with no loss nor duplication). This link may be among -others a named pipe in the Unix environment, a DECNet link and of -course a TCP/IP connection. - -

- -The upper layer use the byte-transport channel to implement a -higher-level protocol: the X protocol. This protocol says how to tell -the server to request window creation, graphics drawing, and so on, -and how the server answers and sends events. The protocol itself is -separated into different parts: - -

How to connect and how to break a connection, -
how to represent the different data types, -
what are the requests and what they mean and -
what are the replies and what they mean. - -

- -[to be continued]. - -

Christophe Tronche, ch.tronche@computer.org

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