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An HPUX 11i network, running on new hardware, for what they call “mission critical” operations at a unique business, terminates for the user at Sherwood 7000STs. While functional (and lightning fast compared to the Web 2.0 systems I grew up with), the terminals connecting via DB-25 (thanks @grawity) RS232 all over the office must be decommissioned. They’ll be replaced with modern Ethernet over RJ45 connections going into a switch with server on a single subnet, and I need to understand how our application will be affected.

SETUP:

Serving an application serially is working fine.

Telnet and SSH are installed.

There are both NIC and COM PCI cards. (LMK if terminology is inaccurate — I will run dmesg tomorrow and update post.)

PROBLEM AS CURRENTLY UNDERSTOOD:

There are many possible configurations of serial terminal.

Telnet and SSH run in terminal emulators when connecting across Ethernet in normal usage.

No firm basis exists for me to expect this application to flawlessly transition.

Previously, server upgrades caused terrible dysfunction between apparently compatible hardware when proprietary wiring meant that our (serial) RJ45 to 25-pin RS232 to 9-pin RS232 conversions had literal crossed wires, as hardware deviated from the spec. Analogies to software are here easy to concieve of, but they should be equally hard to encounter in production!

@Bob - a switch will be in place. What other considerations must I make? See below.

QUESTIONS:

  1. Should I expect telnet to “just work” on a new Linux box (like Raspberry Pi), going into the server? It will be going through a switch, of course. But can Ethernet networks replace serial networks as a drop-in at every layer, up to and including applications?

  2. Baud rate will obviously no longer be necessary, but what about other configurable settings such as escape characters?

  3. Line wrapping?

  4. Paging?

  5. Important: What about programs that define terminal display (such as Unibasic)?

  6. Important: Will RJ45 run the risk of being somehow “incompatible” with the existing system?

NOTE

I am confused where processing takes place, and any deeper characterization of the issues above in this context would be appreciated. Mods, please accept this vague question due to the lack of existing discussion on Stack Exchange. I have carefully looked before posting. I am happy to document my research of the existing lit.

Thank you so much.

lettucehead
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1 Answers1

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You need to be aware that on the HP-UX side, RS-232 interfaces are totally different from network interfaces, which are again different from the telnet API.

If all you use your terminals for is to log in into the HPs, then you can replace that by telnet, or by ssh if you want it to be more secure.

If you have custom software that these terminals connect, then this could be a major problem: You'll have to adapt the software to deal with the new kind of connection. Which, depending on the software, may be easy, hard or impossible, but it's the major concern here.

To the questions:

1) Yes.

2) Won't matter, everything is passed through. If you use it to log in, you can still change backspace/del etc. via stty (if that's what it's also called on the HPs, been too long since I used one).

3,4,5) Is a function of the way the application and the terminal program interpret control sequences. Transport doesn't affect this.

6) See above.

You should keep in mind that processing works on layers.

RS-232 and Ethernet ("RJ-45") are very different transport technologies, as are protocols (telnet, ssh) that work over Ethernet. You should have someone who is familiar with modern network technology, and can install all this for you. If you don't have one, hire one, or ask another company to do it for you.

Above this transport layer, when the software on both sides just sees a character stream, the differences are minimal.

dirkt
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