Well, I guess the proposal was to write a piece of software that a TN3270 client connects to and is able to exchange data with it. I think that's a neat idea, especially as that removes the dependency on ancient hardware that I don't currently have. You say TN3270 merely encapsulates 3270, which makes this a good idea AFAICS.
On Tue, Jan 14, 2020 at 07:46:44PM +0000, Seymour J Metz wrote: > You don't talk TN3270 to an emulator; all of the 3270 simulation is in the > TN3270 client. Tn3270 just encapsulates 3270 data streams and associated > housekeeping. > > > -- > Shmuel (Seymour J.) Metz > http://mason.gmu.edu/~smetz3 > > > ________________________________________ > From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> on behalf of > Charles Mills <charl...@mcn.org> > Sent: Tuesday, January 14, 2020 10:23 AM > To: IBM-MAIN@LISTSERV.UA.EDU > Subject: Re: Talking to 3270 terminals? > > Would talking the TN3270 protocol to a 3270 emulator do the job for you? > That solves all of the hardware issues: it is simply TCP out of your > implementation and into the emulator. > > You could then if you wished "graduate" to a real 3270 terminal. If I were > doing it I would go SNA but that is because once upon a time I knew SNA at > the bit level, but little about how bus & tag worked at that level. > > I can't speak much to physical connection or the layer immediately above > that but this book > http://secure-web.cisco.com/1NJfAPk9CmbKpO7wNkHn9B6nE4DIuDh8VjmoRD6W14LTnkYRS8mUF9pSaMLpoFNQw1X7bKTufSQxpDFbxWiK_GJYC4fCTMeYoNXrWdY006d3QvNX5gwLKr_Tddhqv6hARKpUa2Ww_M-j3EtEtqgNXVwwhqxhBwkNHfbHZNfctAXcxWr7RaxxyYllBigY0HWHt1hks74ObW0Emd3pHjWjCQHpzxYI6aytGZbSKExfPlNvoHUHfwOnPOHU_wmz_J3R0OqSaVHen3cuw0dZztcIwamLWVnT8OOQTiI77EDcb1tWEj5cBj7OzyBwA6w6iZON7Ri3ukxOmPLHqij2zcSk4cUnQ_K-sX-tj8NSLSBvFxasoFny16vytF4hNgcCM-jBg6miye3bvKK4X5b8TCMWs7yI2ByD6-70MEZGk2McpqNsWtMdhCMLw_4RLIurdIAR8/http%3A%2F%2Fruelgnoj.co.uk%2F3270%2F3270.pdf > is the bible of the > byte stream going to the device. > > There is no real reason you could not drive one from Linux or Windows. A > Raspberry Pi with a 3270 attached would be an amusing idea. > > BTW, RS232 is a specification for the plug between a device and a modem. It > is at a lower level in the stack than most of the other things you mention. > Yes, it would be relevant to a dial-up SNA implementation. The "bits going > over the modem" layer of SNA is called SDLC > (https://secure-web.cisco.com/18c0BA4dtXGJ3jrmHxOb0fQfMOn7KsS3MCPwA3S8XLeEpnbvImAU6lrPFliVgZUwfdITCv2vD8QAyQIst3e9t4oQBI5fw6kn3Z5zvTgtodVYMWXfgRrZ_rDOHCTuoC9voavt2oVRuk2rXTFzrTcGuqP2njC-JbLJOzNAFUOz_790kOT5eusVJPhfplzNyOqiC-BBSmblQkv6CG1UkI3YxnfLa6Bh_I3qU4A1_sCKjFd31oN7FM6cohvAz-j8TsK3jjrajkQ4gi3GT8bcI4tjYJ4-8v0X7FsTJ9-lesmTEaWHX0JEhBPROGC5-Psii1-zu50IIMKHtMOJ68yp_bmrKiDcLeI-jUnK_rg6t38XQ7mp3DWnrpndTasniJpzPJ4yk1XewnqlxgXQ_oMJ423_1em3a2ThaJg9sIN_pZIMYnHPGn7lUOGfPv6DNpk7G8fpp/https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FSynchronous_Data_Link_Control%29. > > Good luck! Sounds like fun. > > Charles > > -----Original Message----- > From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU] On > Behalf Of Alexander Huemer > Sent: Tuesday, January 14, 2020 1:52 AM > To: IBM-MAIN@LISTSERV.UA.EDU > Subject: Talking to 3270 terminals? > > Hi > > I am new to this list and would like to discuss an idea and ask several > questions. > > * Did anybody ever attempt to 'talk' to 3270 terminals with something > different than an IBM mainframe? > > 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. > > 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. > > * What's the best available documentation regarding 3174 models and > their features? > > 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? > > Bus&Tag doesn't seem to be a good candidate, it's difficult to interface > with as far as I understand. > Ethernet is way more common these days than Token Ring, though TR NICs > are easy to procure second hand and protocol support under Linux (the OS > I am most savvy with) is in place. > RS232 is easy to interface with also, though then again, I am not sure > if that interface really exists. > > * Did the LAN interfaces (Ethernet, TR) talk SNA on layers 2 and 3 or > was there by any chance something going on with TCP/IP? I doubt it > though. > > Talking SNA with custom software doesn't seem to be a low-hanging fruit. > From where I stand right now I cannot say how straight-forward the > network traffic between the mainframe and a 3174 is, how difficult it > would be to emulate that protocol with custom software over several > layers. > > * 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 would appreciate any thoughts regarding this topic, especially to the > questions marked with asterisks. > Also, if anything is known regarding a similar thing with 5250 instead > of 3170 terminals, that would be interesting as well. > > -Alex > > ---------------------------------------------------------------------- > 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 ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
