[Simh] Way out idea for simh

[Sampsa Laine]

> On 21 Apr 2016, at 01:05, Johnny Billquist <bqt at softjar.se> wrote:
> 
> On 2016-04-20 22:35, Sampsa Laine wrote:
>> 
>>> On 20 Apr 2016, at 23:25, Phil Budne <phil at ultimate.com> wrote:
>>> 
>>> Ken.Cornetet wrote:
>>>> I guess I need to shout this:
>>>> ******* KERMIT DOES NOT WORK ON SIMH EMULATED RTE-6/VM ********
>>> 
>>> Why not?
>>> 
>>>> Kermit does not exist (and probably couldn't feasibly exist) on any earlier versions of RTE.
>>> 
>>> Again, why not?
>>> 
>>> Having just written a new shell for PDP-7 UNIX (because the original
>>> could not be found), I can't imagine much other than a lack of
>>> something resembling a serial console that would prevent _some_
>>> version/subset of KERMIT (or something similar like X or ZMODEM) from
>>> being cobbled together.
>>> 
>> 
>> And since the connection can be assumed to be lossless, the protocol could be really simple, e.g. something like this:
> 
> Actually, we should not assume the connection is lossless, so I would stick with Kermit.
> 
> (There are examples of overflowing the serial port, resulting in lost characters by simple buffer overruns.)
> 
> Add checksums to the packets, and this is pretty much what Kermit is.

Agreed, add a checksum and the built-in SIMH file server sends a NAK if it didn’t like a packet. Each packet is let’s say X bytes + checksum.

I think the generic simple file server should be fairly simple to write and the guest OS tools relatively portable, you just have to change the writing/reading of the metadata for each guest OS.

Of course you only implement this for simulations where Kermit is not an option..

Sampsa

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