I am aware of hercules, an amazing piece of software. Though I am more looking for a dedicated piece of software just to talk to terminals, not as part of a S3*0 OS.
> I think I've recently read some articles where someone is trying to > use a 3270 as a terminal for a Unix (Linux?) workstation. If you could provide a pointer to that, that would be much appreciated! > I think I've recently read some articles where someone is trying to > use a 3270 as a terminal for a Unix (Linux?) workstation. Even more stunning. I am eager to read more. > I think I've recently read some articles where someone is trying to > use a 3270 as a terminal for a Unix (Linux?) workstation. Possible, I didn't check. Though running Linux kernels from the 3.x era isn't what I would consider painful. > SNA is decidedly NOT TCP/IP. That's well understood. I just wondered whether they might have been a communication scheme between an 3174 and a mainframe over Ethernet or Token Ring that used TCP/IP instead of SNA. But again, I doubt it. Thanks for your thoughts. I will consider spamming the hercules mailinglist also. On Tue, Jan 14, 2020 at 06:07:19PM -0700, Grant Taylor wrote: > On 1/14/20 2:52 AM, Alexander Huemer wrote: > > Hi > > Hi, > > > I am new to this list and would like to discuss an idea and ask several > > questions. > > Welcome. > > > * Did anybody ever attempt to 'talk' to 3270 terminals with something > > different than an IBM mainframe? > > Yes* > > * because it's highly dependent on what you mean by "IBM mainframe". More > specifically if you mean the hardware and / or the software. > > I know that there are people actively working in the Hercules community to > drive (talk to) 3270 terminals. > > I think I've recently read some articles where someone is trying to use a > 3270 as a terminal for a Unix (Linux?) workstation. > > So, "It depends...." > > > This might sound like a strange idea, though I find it intriguing to be > > able to display content on such a terminal and be able to receive > > keyboard input from it. > > It doesn't sound completely crazy to me. It does some completely atypical. > But atypical can be entertaining and / or educational. > > > I guess the most straight-forward way to attempt something like that is > > to use a 3270 terminal attached to a 3174 or similar and try to talk to > > that instead of the terminal itself. I wouldn't know how to interface > > with the terminal directly over the coax. > > I believe the article I recently read was talking about driving the signal > on the coax. > > I typically see some variation of the following discussed: > > 1) 3270 terminal talks to the (remote) 3174 Control Unit (?). > 2) The remote 3174 CU talks across Ethernet or Token Ring or RS-232 > something else acting like a local 3174 CU. > 3) This thing acting like a local 3174 usually talks TN3270 to a mainframe > OS, be it running on a physical mainframe or emulated. > > I believe that some later / feature rich 3174s have the ability to act like > primitive telnet clients. Thus you could use the 3270 to talk to a Unix > box. > > > * What's the best available documentation regarding 3174 models and > > their features? > > I don't know. > > I've seen quite informative discussions about this type of thing on the > hercules-390 and cctalk mailing lists, plus a few newsgroups. > > > I poked around on ibm.com and google but wasn't able to find much. It > > seems like there were several different physical-layer north-bound > > interfaces for 3174. Bus&Tag, Token Ring, Ethernet, RS232 (if I am not > > mistaken, for dial-up connections), maybe others? > > I think it's highly dependent on if it's the "local" or "remote" 3174. > > I think that the "local" 3174 was exclusively Bus & Tag for northbound. — > I've not heard of any ESCON interfaces for 3174. — The Token Ring / > Ethernet / SDLC / RS-232 was southbound to talk to "remote" 3174s. > > Similarly, the "remote" 3174 was Token Ring / Ethernet / SDLC / RS-232 for > northbound and coax for southbound. > > The Token Ring / Ethernet / SDLC / RS-232 was used to connect "local" and > "remote" 3174s. > > > Bus&Tag doesn't seem to be a good candidate, it's difficult to interface > > with as far as I understand. > > Two things come to mind to interface with B&T. The B&T cards that exist for > PCs running things like the PC/370 / P/390(-E) or something like a big iron > Cisco router with a Channel Interface Processor card. But I think even the > CIP is a "grey" downstream device and can't pretend to be a "black" host > (mainframe) device. > > > Ethernet is way more common these days than Token Ring, though TR NICs > > are easy to procure second hand > > Agreed. > > > protocol support under Linux (the OS I am most savvy with) is in place. > > Be careful there. Contemporary Linux (4.x) no longer includes Token Ring > support. I believe it was removed from 3.5. > > Even then, there are other protocols that I've not been able to find support > for in Linux. SNA being the biggest contender. There are pieces that I > think could be used to help support SNA. But I'm not sure that all of the > requisite pieces are there. LLC is questionable. There were a couple of > implementations for some different things. I don't know if any of them were > ever complete enough to support SNA. > > > RS232 is easy to interface with also, though then again, I am not sure > > if that interface really exists. > > I think that the 3174s did have RS-232 support. But I'm not sure what it's > purpose was. I don't know if it was for dial up SNA or if it was for > synchronous modems / X.25 networks. > > > * Did the LAN interfaces (Ethernet, TR) talk SNA on layers 2 and 3 > > I think so. > > My understanding is that SNA on Ethernet / Token Ring used 802.2 LLC frames > (you can find the SSAP / DSAP numbers). I don't think that SNAP was used. > > SNA is as different from TCP/IP, IPX/SPX, AppleTalk, etc, as they were from > each other. > > You quickly get into the fact that traditional SNA thought it was the center > of the universe and the only form of intelligent life. Then — as I > understand it — you start getting into APPN when systems are no longer the > center of the universe where there is something out there intelligent like > another host. > > > was there by any chance something going on with TCP/IP? I doubt it though. > > SNA is decidedly NOT TCP/IP. > > That being said, I know that TCP/IP can carry SNA traffic in a myriad of > ways. TCP/IP can encapsulate SNA; SNASw and Enterprise Extender come to > mind. TCP/IP can gateway some of the higher SNA application layer traffic > and carry it more natively; TN3270 comes to mind. > > I've heard / read that SNA could carry TCP/IP traffic via things like AnyNet > from IBM. > > This quickly devolves into a quagmire where you need to really understand > what you do (not) have and what you want to (not) do. > > I believe you can substitute IPX/SPX in place of TCP/IP and have a different > quagmire too. I know that Apple played in this space, but I'm not sure how > much they did on the network layers. > > > Talking SNA with custom software doesn't seem to be a low-hanging fruit. > > No, not at all. > > SNA is a *FULL* *PROTOCOL* *STACK* / *SUITE*. > > You really are talking about all of the layers of the OSI model. > > > From where I stand right now I cannot say how straight-forward the > > network traffic between the mainframe and a 3174 is > > I think that considering it to be a network protocol is probably a > disservice. > > The host sees things connected to it like a tree of devices. Much like USB > on contemporary systems. > > Is it a protocol? Probably. > > Is it a /network/ protocol? I think not. > > > how difficult it would be to emulate that protocol with custom software > > over several layers. > > Probably quite. > > There is a *LOT* to SNA. > > > * Is anybody on the list here able to provide protocol traces from the > > link between mainframe and 3174 over any interface? pcap format is > > preferred, though anything would be valuable. > > I think anything like that over B&T is nigh impossible. > > Yes, it would be possible to get packet captures of SNA over Ethernet or > Token Ring. But I've not seen such discussed anywhere. > > I suspect it would be problematic to find someone with the proper equipment > to configure an RS-232 based connection, much less capture it. > > I think that the further you get away from the host the less of the protocol > that you might actually see. > > I want to say that the host and it's 3174s had a symbiotic relationship. > But that's not the case. It's more that the host was the brain and that > everything else was a lowly appendage. Some things like the 3174 control > units were quite important, like the heart and lungs. But they were still > functionally subservient to the host. > > > I would appreciate any thoughts regarding this topic, especially to the > > questions marked with asterisks. > > This is all my understanding that I've manged to pick up over the last year > or so. It is quite likely that I'm misunderstanding things completely or > may have some subtle nuance wrong. Please politely correct me if I'm wrong. > > > Also, if anything is known regarding a similar thing with 5250 instead > > of 3170 terminals, that would be interesting as well. > > I don't know if I've seen anyone trying to talk to 5250 terminals like > 3270s. But my ignorance doesn't preclude such from existing. > > I was recently involved in discussions about how to leverage different Cisco > routers with proper IOS support to get AS/400s talking to each other across > disparate networks. Enterprise Extender running on a contemporary machine & > OS using an OSA to connect to one Cisco. That first Cisco gatewaying to > something else across virtual Token Ring (?) to another older Cisco. That > second Cisco was doing additional gatewaying to talk to an older machine & > OS on Token Ring. It took the combination of the two Ciscos, each doing a > piece of the job, to allow the two machines talk. > > Search for the "SNA and I Systems" thread in the comp.sys.ibm.as400.misc > newsgroup if you are interested to know more. > > Finally, I'll say that I'm somewhat surprised to see this type of discussion > in IBM-MAIN. Not because I think it belongs elsewhere. Because I think that > IBM-MAIN is more day to day production support related issues and virtually > nobody is running anything like this in production. I would sort of expect > to see this type of discussion in hercules-390 / cctalk / newsgroups that > are further off the beaten path. > > > > -- > Grant. . . . > unix || die > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
