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Unformatted text preview: erver process, which in turn manages the windows on the display. Not shown here is that
the X server also manages the keyboard and mouse. Figure 30.2 Three clients using one display.
This design, where a single server handles multiple clients, differs from the normal TCP
concurrent server design that we described in Section 18.11. The FTP and Telnet servers, for
example, spawn a new process each time a new TCP connection request arrives, so each
client communicates with a different server process. With X, however, all clients, running on
the same host or on a different host, communicate with a single server.
Lots of data can be exchanged across the TCP connection between an X client and its server.
The amount depends on the specific application design. For example, if we run the Xclock
client, which displays the current time and date on the client in a window on the server,
specifying an update of once a second, an X message is sent across the TCP connection from
the client to the server once a second. If we run the X terminal emulator, Xterm, each
keystroke we type becomes a 32-byte X message (72 bytes with the standard IP and TCP
headers), with a larger X message in the reverse direction with the character echo. [Droms
and Dyksen 1990] measure the TCP traffic between various X clients and one particular
A handy program for examining what's exchanged between an X client and its server is file:///D|/Documents%20and%20Settings/bigini/Documenti/homenet2run/tcpip/tcp-ip-illustrated/other.htm (8 of 11) [12/09/2001 14.47.58] Chapter 30. Other TCP/IP Applications Xscope. It's provided with most X window implementations. It sits between a client and
server, passing everything in both directions, and also deciphering all the client requests and
server replies. Figure 30.3 shows the setup. Figure 30.3 Using xscope to monitor an X connection.
We first start the xscope process on the same host as the server, but xscope listens for
TCP connection requests...
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This test prep was uploaded on 04/04/2014 for the course ECE EL5373 taught by Professor Guoyang during the Spring '12 term at NYU Poly.
- Spring '12