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Unformatted text preview: ings/bigini/Documenti/homenet2run/tcpip/tcp-ip-illustrated/telnet.htm (4 of 26) [12/09/2001 14.47.45] Chapter 26. Telnet and Rlogin: Remote Login Sometimes, however, the application running on the server needs to interpret each byte of
input, and doesn't want the client looking at the input bytes and treating Control-S and
Control-Q specially. (The emacs editor is an example of an application that uses these two
characters for its own commands.) To handle this, the capability is provided for the server
to tell the client whether or not to perform flow control.
A problem similar to flow control occurs when we type the interrupt key (often DELETE
or Control-C), to abort the process currently running on the server. The scenario is similar
to what we show in Figure 26.3, with up to one window full of data in the pipe from the
server to the client, while the interrupt key makes its way across the connection in the other
direction. We want the interrupt key to terminate what's being displayed on the screen as
quickly as possible.
In both this case and the flow control scenario, it is rare for the flow of data from the client
to the server to be stopped by flow control. This direction contains only characters that we
type. Therefore it is not necessary for these special input characters (Control-S or interrupt)
to be sent from the client to the server using TCP's urgent mode.
Window Size Changes
With a windowed display we can dynamically change the size of the window while an
application is running. Some applications (typically those that manipulate the entire
window, such as a full-screen editor) need to know these changes. Most current Unix
systems provide the capability for an application to be told of these window size changes.
With remote login, however, the change in the window size occurs on the client, but the
application that needs to be told is running on the server. Some form of notification is
required for the Rlogin client to tell the server that the window size has changed,...
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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