Hello there, I'd like to ask you about the following - is it possible to have multiple serial consoles coming from a single host? What I am talking about is connecting multiple machines using a null modem cable - I know it is possible only to connect two machines and they need to be connected on sio0 (COM1). I'm thinking about the following situation - 1 system acting like a host with a serial port hub, each port of the hub is connected to a different machine on sio0, using null modem cables. This would make the first machine something like a cheaper kind of a terminal concentrator :) What do you think, have someone tried this and is it possible at all? Thanks and regards, DNAeon
On Tue, Jan 12, 2010 at 05:14:44PM +0200, Marin Atanasov wrote:> Hello there, > > I'd like to ask you about the following - is it possible to have multiple > serial consoles coming from a single host? > > What I am talking about is connecting multiple machines using a null modem > cable - I know it is possible only to connect two machines and they need to > be connected on sio0 (COM1). > > I'm thinking about the following situation - 1 system acting like a host > with a serial port hub, each port of the hub is connected to a different > machine on sio0, using null modem cables. > > This would make the first machine something like a cheaper kind of a > terminal concentrator :) > > What do you think, have someone tried this and is it possible at all?What you're describing is basically the concept of a serial console server, where a FreeBSD box contains a multi-port serial card that's connected to multiple other servers. An individual would get on the FreeBSD box with a multiport serial card (see below) and attach to the serial port associated (wired to) whatever other box they want to log on to. Yes this is possible with FreeBSD -- but you'll need to purchase a multiport serial card that's supported natively by FreeBSD. The two I'm familiar with are Cyclades and DigiBoard, but this would've been back in the day of FreeBSD 2.2.x and I've no idea what people use present-day. I'm certain others here can recommend stuff that works. But my personal/professional opinion is that you consider purchasing an actual serial console server rather than "hack up" a FreeBSD box. Most serial console servers these days (and even old Portmasters) can do serial-to-TCP association, which allows you to literally do "telnet consoleserver NNNN" where NNNN is a TCP port which is bound to a serial port connected to each individual server. E.g. port 2000 = box#1, port 2100 = box#2, etc.. As far as present-day devices go, the ones I can recommend are the LX-series devices[1] from MRV Communications. They're Linux-based, and although may seem expensive (16-port w/out modem = ~US$1400), are a one-time purchase. Cyclades also makes identical devices, but they cost something like US$3000-4000, and they wouldn't provide me with a test/demo unit so I blew 'em off. You can also consider looking for used hardware -- either Xyplex devices (MRV bought Xyplex), or Portmaster[2] products. I believe Cisco made some devices as well. WRT Portmasters, be aware that some of the firmware images are spotty in quality (HELP commands missing, undocumented commands, etc.). There's two ports which can make interfacing/using these devices, or a multiport serial card, much easier -- Conserver[3]. I work with the guy who wrote it, so I'm biased. :-) ports/comms/conserver ports/comms/conserver-com I'm not sure what the first port is to be honest, but the 2nd port is what I'm used to using with an MRV LX-4016S device. If you'd like a bit more detail about "how it all works" (the software, the hardware, configuration details, wiring, etc.), I can describe it in greater detail. Just ask. [1]: http://www.mrv.com/oobn/ [2]: http://portmasters.com/ [3]: http://www.conserver.com/ -- | Jeremy Chadwick jdc@parodius.com | | Parodius Networking http://www.parodius.com/ | | UNIX Systems Administrator Mountain View, CA, USA | | Making life hard for others since 1977. PGP: 4BD6C0CB |
Hi Marin, I'd like to ask you about the following - is it possible to have multiple> serial consoles coming from a single host? >In theory, no :-) RS232 is a point-to-point connection. If you want to feed several consoles through the same serial port, you will need some kind of switch to route the traffic to the corresponding port (whether the cable needs to be null modem or not wil depend on the switch itself). What I am talking about is connecting multiple machines using a null modem> cable - I know it is possible only to connect two machines and they need to > be connected on sio0 (COM1). > > I'm thinking about the following situation - 1 system acting like a host > with a serial port hub, each port of the hub is connected to a different > machine on sio0, using null modem cables. > > This would make the first machine something like a cheaper kind of a > terminal concentrator :) >The options that come up to my mind are: - a mechanical switch but it would not allow seamless routing (requires operator action to change channel) - a software switch using ESCAPE codes to change channel through an ad-hoc device driver - but there, make sure you don't miss bytes or the traffic may end up on the wrong terminal - if you fancy a home design, you could use the parallel port to send an address word but you will have to design your own seial port emulation on top of the standard sio0 to synchronize the signals... I would not bet too much on this one ;-) Also, evaluate if you need priority management: you may get to a situation where you need to send urgently characters to a terminal while another one has a long queue pending. In this case, you may be better off with Ethernet-to-Serial or USB-to-Serial converters. Hope it helps Cheers -- Olivier Gautherot olivier@gautherot.net Cel:+56 98 730 9361 www.gautherot.net http://www.linkedin.com/in/ogautherot
On Tue, 12 Jan 2010 17:14:44 +0200 Marin Atanasov wrote:> I'm thinking about the following situation - 1 system acting like a host > with a serial port hub, each port of the hub is connected to a different > machine on sio0, using null modem cables.Along with milti-io serial cards we use multi-usb serial converters, such as SUNIX UTS7009P (7 USB to serial adapter): http://www.sunix.com.tw/it/en/LinkCraft/UTS4009P_UTS7009P.htm -- WBR, Boris Samorodov (bsam) Research Engineer, http://www.ipt.ru Telephone & Internet SP FreeBSD Committer, http://www.FreeBSD.org The Power To Serve
On Tue, 2010-01-12 at 17:14 +0200, Marin Atanasov wrote:> Hello there, > > I'd like to ask you about the following - is it possible to have multiple > serial consoles coming from a single host? > > What I am talking about is connecting multiple machines using a null modem > cable - I know it is possible only to connect two machines and they need to > be connected on sio0 (COM1). > > I'm thinking about the following situation - 1 system acting like a host > with a serial port hub, each port of the hub is connected to a different > machine on sio0, using null modem cables. > > This would make the first machine something like a cheaper kind of a > terminal concentrator :) > > What do you think, have someone tried this and is it possible at all?I have a dozen UBS2serial (uplcom) up 24/7 over more than 6 months, on 8.0 (NanoBSD on ITX-board) in our serverrooms. They work pretty stable and are dead cheap. Max 20 Euro per line, including a null-modem adapter. like: http://www.gridconnect.com/numomatomadb.html or http://www.buyextras.com/numoaddb9fef.html I payed about ~3 dollars per adapter. (shipping to Europe was most expensive) Kind regards, Marten> > Thanks and regards, > DNAeon > _______________________________________________ > freebsd-stable@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-stable > To unsubscribe, send any mail to "freebsd-stable-unsubscribe@freebsd.org"-- http://www.voedselbankleiden.nl needs your help! http://martenvijn.nl http://bsd.wifisoft.org/nek/ http://opencommunitycamp.org OCC 2010