[Simh] Way out idea for simh

[J. David Bryan]

On Wednesday, April 20, 2016 at 20:15, Ken Cornetet wrote:

> I guess I need to shout this:
> 
> ******* KERMIT DOES NOT WORK ON SIMH EMULATED RTE-6/VM ********

I've never used Kermit under RTE, but today I tested the HP2100 simulator 
with two of the Kermits available in the HP CSL (Contributed Software 
Library) -- revisions 2830 and 4230 -- and the latest version of RTE-6/VM 
(revision 6.2).  I used Crosstalk by Attachmate as the simulator's MPX 
device terminal client, which supports Kermit in the server and non-server 
modes.  As far as I can tell, binary and text uploads and downloads work as 
expected.

Crosstalk's Kermit uses the 94-byte maximum packet size by default.  If I 
increased this to match the 2048-byte maximum size supported by the 4230 
version of Kermit for RTE, file uploads failed.  If I decreased the packet 
size in Crosstalk to 250 bytes, uploads worked fine.  Downloads worked fine 
with either maximum packet size.

An upload packet size of greater than 254 bytes would overflow the MPX 
device's receive buffers.  The multiplexer is designed to handle this by 
returning a "partial buffer" status flag whenever a read terminates because 
of a buffer full condition and then returning the remainder of the data on 
the next read call, but it's possible that this isn't working correctly.  I 
am investigating.

However, if the client's packet size is limited to 254 bytes or less, 
Kermit seems to work fine under RTE.

                                      -- Dave