Using an NTS instead of the local serial device ?

Hi folks,

I just successfully set up a basic ppp link between 2 Ubuntu 7.10 machines.

The commands look like this:

me@machine1 $ pppd -detach persist lock proxyarp 192.168.10.1:192.168.10.2 /dev/ttyS0 38400 &

me@machine2 $ pppd -detach persist lock defaultroute 192.168.10.2:192.168.10.1 /dev/ttyS0 38400 &

I wonder whether it is posible to use a serial port of an NTS for communiction instead of the local serial device /dev/ttyS0 ? I own a Lantronix ETS8P, which is a 8-port Network Terminal Server.

I tried

me@machine1 $ pppd -detach persist lock proxyarp 192.168.10.1:192.168.10.2 ip.of.nts:tcpport 38400 &

without success.

As I am new to Linux in general, maybe somebody can give me a hint.

Thanks

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I do not think PPPD can connect to a terminal via the method you tried. What you need to do is load the Lantronix virtual serial port software on both servers and setup a pseudo serial port. Tell pppd to use that instead. It should work but why not just use the network and create PPPD over an ssh ssh tunnel instead of using a terminal server to begin with. Why are you using a termianl server anyway? Can't the machines communicate over the network?

Also look at OpenVPN and Vtun. You can create pppd links using pseudos that way too.

It *might* be possible to get pppd to talk to the terminal server using the -socket option, but it would depend on what protocol the terminal server talks across the network. Can you give us any details on that protocol?

Paul.

After browsing the support sites of Lantronix, I think I found the software I need:

The rtelpd daemon process is used to provide access to
serial or parallel ports on a terminal server. A named
pipe is used as the actual interface to host based appli- cations. These applications can then communicate with equipment attached to the server as if it was locally attached to the unix host.

I can create a /dev/somepipename device with that tool.

I need this rather unconventional method because we have several remote sites that are connected to the center via public digital lines (64k). Multiplexer on each end offer up to 16 transparent serial RS232 ports. Via the ppp link we get access to the network in the center- it's slow but sufficient for our application.

The NTS is only needed in the center because it offers 8 ports. I find this more elegant than upgrading the Ubuntu- Server with additional serial ports.

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If there was a -socket option, I'd like to try. But I can't find a -socket option neither in the man pages nor in other documentation about pppd.

# pppd: unrecognized option '-socket'

Here at home I have a Suse 10.1 linux with pppd version 2.4.3 installed.

The serial ports on the Lantronix are easily accessable- e.g.

# telnet 192.168.0.1 2003

will write everything that's being typed to physical port 3, and everything that is being receveid on that port 2 is displayed in the telnet window

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I do not think my version of pppd supports that either. What you need is the software that will create link a pseudo tty in each system to the terminal server and then you can run pppd on each side.

http://demo.opsdc.com/atlpm/ttyd2.pl

I wrote that for a friend to map some pseudos on a SUN box to another terminal server. It may need some tweaks but should map a pseudo on Linux to a port on the TS.

Sorry, it's "socket" (no dash) and it takes an argument which is host:port. However, if the Lantronix really does the telnet protocol then it won't work properly since telnet interprets the 0xff character and CR (0x0d) characters specially.

If you can put the terminal server into a mode where everything received on the socket is sent to the serial port, without interpretation, and everything from the serial port is sent on the socket, without modification, then you could use it with the pppd "socket" option.

Paul.

Lantronix devices support both. You connect to 2000+n to get TELNET protocol (with the 0xff escapes), and 3000+n for a raw TCP connection.

So, for port 1, use this in pppd:

	socket ip-address:3001

(Most other terminal servers have similar features. For example, the equivalent ranges on Annexes are 5000+n for TELNET and 7000+n for raw TCP.)

I would advise the original poster to avoid reverse telnet. It may work with some applications, but it's a frightening bit of hackery that (at least in my experience) often fails in strange ways.

James Carlson         42.703N 71.076W         <[email protected]>