HTML Emulation WAS: 5250 Data Streams

Pete,

I scanned the Javadocs for SS-OHIO at:

http://os-ohio.sourceforge.net/javadoc/index.html

The os-ohio interface looks like it was designed for Applets or stand-alone
applications rather than Servlets, but maybe it could be adapted.

A single instance of a Servlet handles requests from multiple concurrent
users, and individual users may need multiple 5250 sessions, but it looks
like the os-ohio components maintain the state of just one 5250 session.

I wrote a small RPG program that dumped the 5250 data stream for the Sign On
screen to a file, then displayed the file in HEX mode.  With the help of
chapter 15 in the 5494 Functions reference, it was possible to see the
format of the data stream.

Two byte escape sequences are used for screen functions like:

X'0440' - Clear Screen
X'0411' - Begin Screen Output

Most of the remainder of the data stream defines screen elements - text
constants, and input fields.  

X'11' marks the beginning of both text constants as well as input fields.
The next two bytes indicate the position (row and column).  The next byte
contains either the display attribute of a text constant, or a byte (x'1D')
indicating the beginning of an input capable field.  The x'1D' is followed
by field attributes, field length, and field value.  Simple screens don't
look to hard to parse.

Hope that helps,

Nathan.




-------- Original Message -----------

date: Tue, 20 Jan 2004 13:29:17 -0700
from: "Pete Helgren" <pete@xxxxxxxxxx>
subject: RE: 5250 Data Streams WAS: Arrow keys + scroll keys

The short answer here is that I don't have enough info at the time to
"report in" although when I have a more functional prototype I can share
here, I'll actually point back to the tn5250j site at Sourceforge where I'll
post the code.  Scott Klement, who responded earlier, actually brought me
full circle: I had started at tn5250j, wandered over to the OS-OHIO site,
built a shell prototype of a 5250 HTML servlet, needed more information on
using and formatting 5250 data and then James and Booth's
knowledgeable-looking posts about 5250 data sparked the thought that they
may have an easier to understand set of documentation for 5250.  So around
and around we go.  For the list's benefit, I am working on the perhaps
Quixotic idea that a 5250 emulator can be built using HTML. NOT like WSG
(which was both ugly and slow) and not screen scraping, just a good, basic,
no bells and whistles 5250 emulator.  The reason: iSeries access is
bloatware at its best (or worst), Mochasoft TN5250 is excellent and cheap
but can't be easily integrated into the HTML and java apps we are working
with, tn5250j is an excellent, open source TN5250 java applet/application
but using a heavy, client-side JVM gives me the "support willies" so rolling
my own for HTML was the option I arrived at.  The lack of open source,
"pure" HTML-based Telnet clients (plenty of applets) tells me that this is
probably a fools errand but, that hasn't stopped me in the past.

The quick impression of OS-OHIO is:  If *I* can write a 5250 servlet
prototype in just a few hours, it must be easy.  Completing the project will
be the true test of it's usefulness though.

Pete Helgren