How to get a Linux machine serially connected to WR21 modem send data out to a dedicated remote server

Terminal: Embedded Linux box
Modem: DIGI Transport WR21
ISP: Either AT & T or Verizon
Remote Server: A Linux or Windows box

Terminal to Modem: Serial
Modem - ISP: GSM

What is our goal?
Terminal (Embedded Linux box) to be able to send data to the Remote Server every 10 minutes.


  1. What ( A ) settings and ( B ) commands can help me accomplish my goal?

Appreciate your help!

Thank you,
Satish M S


if you are trying to talk to a device over the internet then you should have a IP port number for the data seen on the serial interface to be sent to the other device.

within the wr21 you can use the multitx function found under Configuration - Network > Interfaces > Serial > MultiTX Serial Ports > MultiTX Serial Port 0

here you can assign the serial interface which in your case would be 0 and the internet IP and port of the other server.

if you need something else then this document might be helpful


I also have another question:

What is the number to use with the ATD command for the modem to connect with the ISP? The ISP being Verizon or AT&T.

Thank you,