Newbie totally lost

we have a pair of machines (m1,m2),each equipped with a 4E1 board; the boards have dahdi drivers for Asterisk.
I’m totally new with everything and I’ve been asked to create a simple software that, running on m1, sends data to m2 via ISDN. I don’t know where to start from.
I’ve managed to test the two 4xe1 boards with loopback cables and installed asterisk on m1/m2. Hardware seems to work properly.
Now, I don’t even know if Asterisk would be the right choice to do what I need.

Can I please get some pointers?
Thank you a lot in advance


So you have 2 boxes each equiped with 4 primary rate interfaces and don’t know how to hook up Asterisk? AFAIK all vendors of these boards have instructions to install the necessary drivers and how to communicate with Asterisk. This is where you should start.

we have two nxmc_4e1 boards: one on each machine.
The board comes with sources which have to be compiled with dahdi.
I followed all the suggested steps to compile and run basic loopback test.
I’ve also managed to get “dahdi show channels” work on asterisk.

Now I don’t know how connect the two machines through the E1 lines: I’m not even sure I should do this with Asterisk.
Let’s say I have to write the simplest program which sends a 4-bytes payload (i.e. “0x00 0x01 0x02 0x03”) from machine 1 to machine 2 through the ISDN connection.

Thank you for your help

I don’t believe that Asterisk supports ISDN data calls.

I don’t think you should be trying to use basic rate interfaces without previous experience.

Thank you sir!
Coul you please spend a few words on the typical approach to this?
As a total newbie I expected to stumble a a few well known and consolidated alternatives for sending data, whereas I’m confuse and cannot find any tools or good basic articles about this

thank you

It’s not something that I have done, and IP over DSL or black box fibre systems, has been the preferred method for over a decade, so direct data over basic rate is now very specialist.

I would contact the manufacturer of the 4E1 board for detailed technical specs. I would see if there’s an open source IP driver for it. Or is the Asterisk driver open source? Probably not, but I wouldn’t assume that before checking.

OTOH if there’ s a network driver, you might just want to use it. Start up a TCP stream and pour the bytes you want to transfer through it. The only reason to program the ISDN “bare metal” IMHO would be if the performance isn’t there to support the packet overhead.

If OTOH you don’t care about performance, and you just need to use the call-setup and routing features to connect one ISDN to the other ISDN, you could try a software modem - say “iaxmodem” to get you a low-performance data stream running over the telephony layer.

Thank you for your contribution!


Hi Jerry,
The boards wereaquired with source code for driver, in particular:

  • driver to be compiled wiythin upstream Dahdi sources
  • standalone driber
  • test application

I managed to compile standalone driver and test application, which consists in a textual interface which runs some loopback test.

I then followed the guilde to compile the dahdi drivers and make sure it is recognized within Asterisk: that took a while, given my unexperience with Asterisk and it was fixed providing the correct configuration files in Asterisk.

I tried to explain my desired setup and I’m still waiting for an answer, so I decided to ask for help in this forum.

Since I’m starting from scratch, I wanted to understand which way to go: Asterisk or standalone drivers.
With standalone drivers, I guess I can start from the monitor application whereas with Asterisk I can follow your suggestion. I wanted to avoid to invest time on a wrong approach

Thank you so much for your feedback


Also, ISDN B channels only support data structured as groups of 8 bits, so, before you can send a string of bytes, you need to define mechanism for delimiting the start and end of those strings.

good to know: thank you


Hi Jerry,
I endedd up following your suggestion which seems to be the best approximation for what I need.
Right now, I’m experimenting with 2 instances of iaxmodem running on the same machine where Asterisk is running; I’ve put together a configuration where

  • I connecto to iaxmode0 and issue “atdt1234”
  • Asterisk shows a call being directed to iaxmodem1
  • I connect to iaxmodem1 (with “cu”) and I see it “RINGING”

my plan is to get this connection working first and then move on and try to perform the connection running though the PRI board (using DAHDI)

Again, I’m totally new to all of this and I’d appreciate your feedback: am I following the proper track?

thank you very much

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