Section 1.6. Communication

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1.6. Communication

The components of a computer system cannot achieve very much when they work in isolation:

• A process may need to talk to a graphics card to display output.

• A process may need to talk to a keyboard to get input.

• A network mail system needs to talk to other computers to send and receive mail.

• Two processes need to talk to each other in order to collaborate on a single problem.

Linux provides several different ways for processes and peripherals to talk to each other, depending on the type and speed of the communication. For example, one way that a process can talk to another process is via an interprocess communication mechanism called a "pipe." A pipe is a one-way medium-speed data channel that allows two processes on the same machine to talk. If the processes are on different machines connected by a network, then a mechanism called a "socket" may be used instead. A socket is a two-way high-speed data channel.

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It is becoming quite common nowadays for different pieces of a problem to be tackled by different processes on different machines. For example, there is a graphics system called the X Window System that works by using something termed a "client-server" model. One computer (the X "server") is used to control a graphics terminal and to draw the various lines, circles, and windows, while another computer (the X "client") generates the data that is to be displayed. Arrangements like this are examples of distributed processing, where the burden of computation is spread among many computers. In fact, a single X server may service many X clients. Figure 1-3 is an illustration of an X-based system.

Figure 1-3. An X server with X clients.

We will discuss the X Window System further in Chapter 10, "The Linux Desktop."