Re: Thoughts in Random Order -- LINUX5250

On Wed, Nov 17, 1999 at 09:45:05PM -0000, wsuetholz@centonline.com wrote:
> Site for 3270 info:  <http://www.tn3270.com/>  <tn3270://tnserver.di3270.com/>
> 
> I have connected to the tn3270 test machine, but it really doesn't have enough
> of a test environment for real world stuff.  How would the tn3270E vs the 
>tn5250
> extended options processing be handled?
> 
> It sounds like you are splitting up the functionality in way very much like 
>the
> way I did it.  You might wish to explore the option of having the telnet 
>portion
> be running in a seperate thread for the datastream portion.  

That would be less portable, for one.  We've handled the concurrency issues
(like the server sending a Message Waiting on message while the terminal is in
a read, for example) by making it event driven akin to the way Win311 use to
work.  Or not work.  Or whatever.   ;)

This way is much more like a simple state machine.

> 
> Have you ever run across a terminal server that has you log in and then 
>switches
> over to datastream mode?  I've noticed that X3270 has the capabilities to do
> this, but I don't know if the same things are done for the 5250 terminals.

There is a generic terminal server piece of hardware kinda deal that
authenticates before forwarding the connection to the appropriate server (or
starting a ppp session or slip or whatever).  That is a somewhat antiquated
way, but remember making dialing scripts that entered user name and password
before you can get a connection to your ISP?  Same piece of hardware - I think
PPP didn't used to have the authentication capabilities built in.  Or slip
didn't, or something.

I imagine that's what it's for.

> 
> On 17-Nov-99 Jason M. Felice wrote:
> > On Wed, Nov 17, 1999 at 05:57:29PM -0000, wsuetholz@centonline.com wrote:
> >> Speaking of thoughts...  It's been a while since I examined the
> >> tn5250 source code in some depth, but, how hard would it be to 
> >> extend the lib5250 to be a generic lib3270/5250 that could handle 
> >> (based on terminal type) the differences between 5250 and 3270 
> >> datastreams.  My code still uses a front end datastream processor
> >> and one or more back end I/O processors.  This is because I am
> >> emulating multiple LU's from one control program.  Screen Scraping.
> > 
> > That would be cool.  I haven't got the hardware to test 3270 emulation, but
> > if
> > you care to donate a small 390, have it shipped to:
> 
> I don't have any host's on site.
> 
> > (Yes, I know the AS/400 can do 3270, but that's not as funny.)
> 
> The way I here it, it introduces quite a load on the system when it does..
> 
> > Doable, and maybe useful (less duplication of effort for things like Gnome
> > support).
> > 
> And maybe possibility for a general purpose terminal library?

That would be good.  I eventually want to add tn5250 server support as well,
and build a patched telnet that can accept 5250 and telnet sessions.  If 3270
isn't too difficult to "reverse", that would be neat, as it would be kinda a
telnet super-server.

> 
> >> 
> >> The basic functions that the terminals use are very similar, it's 
> >> just that they use different opcodes to accomplish those functions.
> >> 

That shouldn't be a big deal at all.   Copy session.c and start hacking ;).
The only caveat would be that functionality that is duplicate between the two
should probably be moved elsewhere instead of copied.

> > 
> > I've often wondered what the reasoning behind this was, did they just design
> > 5250 to handle more processing on the client end, or what?
> 
> I haven't really noticed that the 5250 terminal has all that much more 
>"smarts"
> than the 3270 terminals,  maybe a few more local edit functions, and more
> function keys.  I really don't see why they had to make a new set of opcodes, 
> reusing some...

Hmm, I was regurgitating an observation made by someone else, but I forget who.
I don't know much about 3270.

-Jay 'Eraserhead' Felice
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