Browse Prior Art Database

Emulation Data Stream

IP.com Disclosure Number: IPCOM000101650D
Original Publication Date: 1990-Aug-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 3 page(s) / 101K

Publishing Venue

IBM

Related People

Lackritz, NM: AUTHOR [+2]

Abstract

Given a networking environment, it is desirable to allow the use of server machines as remote processors executing interactive applications accessible from end-users' desktop workstations. In implementing such a scheme, it is necessary to define the communication protocol or datastream that flows between a user's desktop workstation and its associated remote computation server machine. This disclosure details the Emulation Datastream (EDS): a datastream that describes the user input received at a workstation and the visual output from the display of the computation server. Emphasis is placed on making a compact and easy-to-decode protocol to prevent significant performance degradation when running applications remotely.

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Emulation Data Stream

       Given a networking environment, it is desirable to allow
the use of server machines as remote processors executing interactive
applications accessible from end-users' desktop workstations.  In
implementing such a scheme, it is necessary to define the
communication protocol or datastream that flows between a user's
desktop workstation and its associated remote computation server
machine.  This disclosure details the Emulation Datastream (EDS):  a
datastream that describes the user input received at a workstation
and the visual output from the display of the computation server.
Emphasis is placed on making a compact and easy-to-decode protocol to
prevent significant performance degradation when running applications
remotely.

      EDS consists of network packets organized as shown in Figure 1.
The two types of network packets are INPUT and OUTPUT. INPUT packets
simply forward a set of keystrokes from the user's workstation to the
server machine.  A leading byte is used to indicate the number of
keys being forwarded.  ASCII escape sequences are used for encoding
those keys with scan codes greater than 127.

      The OUTPUT packets encode screen updates occurring anywhere on
the server machine's display and forward this information to the
user's desktop workstation where it can be used to update a
corresponding screen image.  Display information is encoded as a
cursor location followed by a length byte.  Next, ASCII character
information is encoded in a word-length format with the first byte
indicating the character and the second byte indicating its display
attribute set.  The server display management program gathers these
OUTPUT packets into a stream which represents all of the changes that
have been made to the server display.  This stream is then forwarded
to the end-user's workstation.

      EDS is built and decoded by related programs running on both
the server and user workstations (see Figure 2).  For keystro...