<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"></head><body><div><br></div><div>Kermit also did some things that were odd.</div><div>I had a goofy modem, an early 2400 baud one. Besides having a hard coded hangup after 5 minutes idle, it would not respond directly if you types +++, it only responsed if the remote system sent that. Kermit didn't give me any problems with it.</div><div><br></div><div id="composer_signature"><div style="font-size:85%;color:#575757">Sent from my Galaxy Tab® A</div></div><div style="font-size:100%;color:#000000"><div>-------- Original message --------</div><div>From: Johnny Billquist <bqt@softjar.se> </div><div>Date: 04/20/2016 4:24 PM (GMT-07:00) </div><div>To: Sampsa Laine <sampsal@gmail.com> </div><div>Cc: simh@trailing-edge.com </div><div>Subject: Re: [Simh] Way out idea for simh </div><div><br></div></div>On 2016-04-21 00:11, Sampsa Laine wrote:<br>><br>>> On 21 Apr 2016, at 01:05, Johnny Billquist <bqt@softjar.se> wrote:<br>>><br>>> On 2016-04-20 22:35, Sampsa Laine wrote:<br>>>><br>>>>> On 20 Apr 2016, at 23:25, Phil Budne <phil@ultimate.com> wrote:<br>>>>><br>>>>> Ken.Cornetet wrote:<br>>>>>> I guess I need to shout this:<br>>>>>> ******* KERMIT DOES NOT WORK ON SIMH EMULATED RTE-6/VM ********<br>>>>><br>>>>> Why not?<br>>>>><br>>>>>> Kermit does not exist (and probably couldn't feasibly exist) on any earlier versions of RTE.<br>>>>><br>>>>> Again, why not?<br>>>>><br>>>>> Having just written a new shell for PDP-7 UNIX (because the original<br>>>>> could not be found), I can't imagine much other than a lack of<br>>>>> something resembling a serial console that would prevent _some_<br>>>>> version/subset of KERMIT (or something similar like X or ZMODEM) from<br>>>>> being cobbled together.<br>>>>><br>>>><br>>>> And since the connection can be assumed to be lossless, the protocol could be really simple, e.g. something like this:<br>>><br>>> Actually, we should not assume the connection is lossless, so I would stick with Kermit.<br>>><br>>> (There are examples of overflowing the serial port, resulting in lost characters by simple buffer overruns.)<br>>><br>>> Add checksums to the packets, and this is pretty much what Kermit is.<br>><br>> 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.<br>><br>> 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.<br>><br>> Of course you only implement this for simulations where Kermit is not an option..<br><br>Well, you have pretty much described exactly how Kermit works. Why not <br>use that then? You do not actually have to implement the more advanced <br>stuff. Kermits can talk to each other, even ones with limited <br>functionality. Also, another thing Kermit can do is escape all <br>characters with the high bit set, and almost all control characters, <br>which can be useful as not all OSes are that transparent on non-printing <br>characters.<br><br>Kermit exists for lots of systems, but if it don't, then writing a <br>simple Kermit is no worse that writing something similar with your own <br>invented protocol. But using Kermit you also only have to implement one <br>side. The other side already exists.<br><br>And despite other peoples comments to the contrary: Kermit is simple to <br>implement. I've done it on a PDP-8.<br>I can't remember, but I might have been using 8K for it. Doubt I used <br>more. And that had some fancy stuff that you don't really need, so a <br>slimmed version could fit in less.<br><br> Johnny<br><br>-- <br>Johnny Billquist || "I'm on a bus<br> || on a psychedelic trip<br>email: bqt@softjar.se || Reading murder books<br>pdp is alive! || tryin' to stay hip" - B. Idol<br>_______________________________________________<br>Simh mailing list<br>Simh@trailing-edge.com<br>http://mailman.trailing-edge.com/mailman/listinfo/simh</body></html>