serial port to ethernet adapter

Do any of you have any experience with this sort of thing? I'd like to control the club's video switcher from a computer that is very far away (since having a computer next to it has turned out to be an expensive pain in the ass.)
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27 Responses:

  1. gorgonous says:

    At work we have ~10 of those types of devices hooked up to our card lock system and EWSD switch. They're pretty simple; just give it an IP and port to listen to, set up the serial port and you're done.

    If the software you use doesn't speak IP, there's utilities out there that will create virtual serial ports and do the serial<=>telnet magic.

    • brianenigma says:

      At work, ship out hundreds of Lantronix devices as daughterboards for various embedded systems. They have both standard ethernet and WiFi. I have to agree, they are pretty brainless and simple but get the job done well. The Lantronix, at least, has an interactive configuration app tied to port 9999 so that you can telnet in and set things like IP, port, and baud. It then listens on 10001 (by default). The first incoming connection on the network side is then tied to the serial port, additional incoming requests to that port get rejected until the one disconnects, at which point it goes back into listen/accept mode.

      The only issues we have ever had with them are: (1) it sort of expects the network side to be a telnet session (sending out the initial telnet 0xff control characters and such) and (2) only one person can connect at a time. They are not big issues, you just have to build them into your architecture.

      (Again, my only experience is with Lantronix, but based on spec sheets, they all look to be about the same.)

      • icis_machine says:

        and i do think those are particularly choice for this type of project, but i don't have experience with either directly, but i regularly use and develop other embedded tools that do similar things for development purposes.

      • pmb says:

        I worked for the company that designed and built the early Lantronix product line - I can vouch for the fact that the MSS line of products is pretty solid and mature. The hardware and software has gone through a whole mess of revisions and contained (when I was last privy to info) no showstopper bugs. The MSS-100 (one serial port to 100BaseT ethernet) is probably what you want, possibly the MSS-VIA if you want wireless. I have no idea about their later products, because they screwed us and so we stopped designing stuff for them and went out of business instead.

        I'm also 99% sure you can disable the telnet 0xff crap, but I totally forget how. "set server software flowcontrol off" or something like that, I'm sure.

  2. waider says:

    Worked with some for a bit about a year and a half back. Mostly they seem to work as you'd expect once you've them set up, and I've played with some upmarket versions which can download their config via TFTP. The particular model I spent most of my time working with could operate as a client or server. Do you have specific questions about 'em?

    • jwz says:

      Mostly I was just wondering whether they worked at all.

      Like, in my dealings with serial ports, I've often found myself in situations like, "the port loses its mind unless you bleed a Kermit over it first". Or "play stupid buffer-flushing-read games for a while after opening the port."

      I was wondering whether this sort of lossage is exacerbated by the extra hardware dingus.

      • waider says:

        Can't say I had any problems with it, to be honest. And it was hooked up to an insanely dumb piece of hardware that was far more likely to lose its mind than the serial/ether doohickey.

      • solarbird says:

        I had some issues like that with an old Xyplex terminal server. It wasn't so bad that it was useless - and as long as your data rate from the ether-side was kept to a minimum it would work out - but it did do some packet shedding if you got too far ahead. I think that just had to do with poor flow-control on the specific Xyplex unit. But trying to talk to the remote device (a modem) to try to configure its firmware and debug was definitely made more difficult by the presense of the telnet-protocol control layer.

        This was an oldish box when we were playing with it - it was made in 1996, I think. Hopefully newer ones are smarter.

        • We use them extensivly, and they are so feature prone they tend to be a pain in the ass. Like, unless you specify, it will not auto-baud with the serial device.

          Most of the problems we have are due to forgetting this fact or something very similar

      • willco says:

        Exacerbated? No, not so much. I used a lot of the Lantronix units - MSS100, I think - and they were pretty much bullet-proof. There are varieties of net.fuckery[1] that can hang the serial session, but you can telnet to the control port, and use the monitor shell there to reset the session. Some of the newer units allow configuration via a built-in web server, too.

        (1) some jackass once configured his workstation with the same IP as the control system, and poisoned the ARP cache on several serial units. Fixing the offending w/s, shooting the jackass in the 'nads, and doing remote resets of the serial connections fixed it all up in a matter of minutes.

  3. quotation says:

    You might want to look at this device, it offers a little bit more than just ethernet-serial.

  4. travisd says:

    How far is Very Far? If there's an existing Cat5 run there you might be able to do it without any devices, or with a serial line driver and not have to change how you talk to the device.

    • jwz says:

      At least 400'. There's not an existing spare cat5 run, but there is ethernet. If I had some reason to believe that doing it without using ethernet was better, I could do a new run, but ethernet kinda sounds more straightforward to me.

    • nester says:

      Interesting point, I bet it would work, even at that distance, provided it was at a low baud rate.

      I know we used to have WYSE terminals all over the building, all connected through what we refer to as "silk" which is that flat 8 conductor wire... I'm sure we've got some runs into the hundreds of feet, and they seemed to work ok..

      I assume it's similar to ethernet.. Those maximum distances are just a suggestion.. not a requirement.. :)

      • travisd says:

        It's probably worth pinning up a couple RJ45<>[DB9|DB25] adaptors and seeing if it works if you can steal the existing ethernet drop for a short period of time. You might even get luck and be able to get away with just 3 conductors (TX, RX, Gnd) and be able to split the pairs on the existing run. Not exactly spec for the ethernet run, but it wouldn't be the first time it's worked...

      • ajaxxx says:

        the distance limitations on RS232 are strictly there for grounding purposes. RS232 uses single-ended signalling, and while it's perfectly possible to run it half a mile across campus, the first electrical spike to come along will move ground on one end away from ground on the other, and one side or both will blow out. within a building it's generally safe to run RS232 absurd distances, even at 115200bps the wavelength is still 4.5km/bit so you don't really run into transmission line effects.

        RS422 uses differential signalling and can therefore be run long distances and between power circuits safely.

  5. jtl says:

    I have one of these and have been pretty happy with it. The picture is incorrect -- this model only has one serial port.

  6. baconmonkey says:

    at the bad place we used a passive serial/cat5-10bT adapter for a 150+ foot run. it won't work over active ethernet, but it worked just fine over an inert long run of cat5. JNA can tell you what the exact model of the dingus was. I'm sure they were a hell of a lot cheaper than $120

    • netik says:

      Ha, it was $5 of those push-in connectors and I made a run ensuring that transmit and receive were on different pairs to eliminate crosstalk. jwz could probably make that work too.

      You might want to try some of the single-port devices that Digi makes. I think you can score them on the 'net for around the same price.

      You'll be looking for the "Digi One SP".

    • bodyfour says:

      If you're going to use a dedicated run anyways why not just run RS232 directly... as above posters described 150' (or even 400') is *not* a problem for RS232 as long as both sides are on the same power feed (so ground is not floating)

      Personally that would be my suggestion, since it eliminates all extra equipment from the hostile nightclub environment. If running an extra cat5 is not practical you could even grab the two unused pairs from an existing 10/100 feed and use them as long as you don't need *any* flow control on the rs232 side (although that sounds a little sketchy to me and is probably more trouble than its worth)

      $120 seems a little steep considering that it's basically just a 1-port terminal server... rs232 terminal servers are pretty cheap these days used (do an ebay search for "livingston portmaster 2e" for example) Of course this 1-port unit might be simpler to setup and/or more reliable under nightclub conditions.

  7. d_foxfire says:

    We use this company's termservers at work for serial console stuff. They seem to get it, and give you the option to do a whole bunch of cool serial< ->network stuff. Their Digi One SP product is probably what you want; it's $147 at CDW, which is the cheapest I've found it. Note that I haven't used or touched this particular model before, just their 'digi CM' termservers.

    If it's like our termservers, though, it's got an embedded linux base, and supports telnetting to a port (with or without the telnet extensions), reverse-telnetting (where the device connects itself to a host/port of your choice), and my favorite, RealPort -- install a driver on your system (win & linux, not sure about others), and the termserver shows up as a local serial port on your system for brain-dead apps that need /dev/cuaX or COM3. All authenticated or not, as you decide. Check out the manual from their support pages too for the rest of what it can do.

    The other stuff mentioned will probably work, but this particular company's stuff seems to be less brain-dead than most. (I don't work for digi, but I like their stuff.)

  8. bitwise says:

    On the cheaper side, you could use RS-232 to RS-422 converters on each end. This is a simple electrical conversion from RS-232, with no sophisticated hardware at all.

    RS-422 uses differential signalling, with a max distance of several thousand feet. You could probably use cat5 cable to do it if you have a lackey willing to wire the connectors. This was a typical solution for stores 10 or 15 years ago who wanted peripherals in another building.

    Another alternative would be to look for a USB serial controller and then use one of the USB-CAT5 extenders. I'm not sure of their max range though; some of them aren't rated past a few hundred feet.

    I think the box you're looking at makes the most sense, though.

    • zkzkz says:

      I think you guys are missing the point. He doesn't have a wire going from point A to point B. He could run one but if he doesn't have to he doesn't want to.

      What he does have is a network that includes ports at point A and B. In between are switches or routers or who knows what. But he can talk IP to a device at point B from point A.

      So the kind of device he showed, basically a one port terminal server, is the simplest solution to the problem if it works.

      I don't know the answer to the question though. It seems like it depends on the complexity of the serial protocol for the device.

      Does the device shown come with two ends so you still have it hooked up to a serial port at the driver end? Or does it have special software for creating a virtual serial port? If it's software does it support the OS you need to have the driver run on?

    • hatter says:

      I'd say much the same - rs422 is the cheap and reliable, zero new problems solution, but I've used several different (multiport) term servers and the only real issue these days that I could see him caring about is making sure the software doesn't swallow any important escape sequences, and that's been pretty solidly eliminated these days.

      There are security issues, that devices doesn't do ssh, at all, and some similar devices only do ssh1, but hopefully a club with semi-visible ethernet drops will already have that addressed. The *nix based terminal servers are generally tweakable to even stick a key pair on

      However, $120 is frankly likely to be Cheap Enough, it increases the flexibility of the unit as he'd be free to locate the host machine anywhere, or even run on different hosts, if that was beneficial.

  9. guyver3 says:

    I used a device like that (not same brand) for my colo at one time, but ended up switching to a cisco cs-516 because it was cheaper once I added more machines, than buying more and more of those. They are easy to use and work as intended, IP access to serial consoles. The model you linked looks a lot slicker than what I had, with all this fancy dhcp and arping and pppoe. Definately good for non-networked equipment, or OOB management for networked.

  10. gchpaco says:

    Once upon a time I bought several network terminals (they are still in my closet) that among other things could do something like this. As network terminals they weren't great because their emulation of VT100 left something to be desired, but I never had any problems with their ability to talk serial or TCP/IP, and I seem to recall setting them up in the manner you intend and having it more or less work. So I'd say it's worth a shot.