AT Modem UDP Client#

This example illustrates an end-to-end communication from a UDP client to a UDP server in a Python environment. It allows to test uplink and downlink packet transmission from a device (a board for the purpose of the Demo) and a destination server.

The device application sends messages to the cloud application on a periodic basis.
The cloud application displays every received message and sends back the message to the device application.
The device application displays every received the message.

The example demonstrates how to use the SCHC SDK using the Datagram API through AT commands with a cloud application expecting IPv6 UDP frames. The demo files can be found in the /at-modem/udp-client/ directory of the lab-schc-examples repository.

cd lab-schc-examples/at-modem/udp-client/
head README.md

Operation#

This example considers a UDP server application with the IPv6 address abcd::1 running on port 22222 and the device configured in the SCHC Gateway with the IPv6 address 5454::2 and a UDP port number 33333.

Build and flash the FullSDK ATModem example application.

cd full-sdk-delivery/
# Build:
cmake -S . -B ./build/ -DAPP_NAME=ATModem \
 -DAPP_VERSION=4.0.0 -DFULLSDK_VERSION=3.0.0 \
 -DTOOLCHAIN=gcc-arm-none -DTARGET=m4 -DPLATFORM=STM32L476RG-Nucleo \
 -DL2_STACK=semtech -DNUCLEO_LORA_SHIELD=SX1272 -DPLATFORM_TRACE_ENABLED=1 \
 -DEXTENSION_API=template -DTEMPLATE_ID=dynamic && make -C ./build
# Erase and Flash:
OPENOCD_TARGET=stm32l4x.cfg make -C openocd/ erase && \
 OPENOCD_TARGET=stm32l4x.cfg BIN_FILE=build/gcc-arm-none/m4/ATModem.bin \
 make -C openocd/ flash

Alternatively, if you prefer using pre-built binaries, visit the AT Modem Firmware repository, where you can find ready-to-use binary files for the supported development boards.

At this point you can already make use of the device as AT Modem and manipulate the stack via AT Commands. Open a serial communication program, such as minicom, and type the AT and AT? AT commands to verify the device is working properly. Close this serial communication before proceding with the demo.

Launch the cloud Python application: the UDP server.

cd lab-schc-examples/at-modem/udp-client/
sudo python3 -m cloud -ip abcd::1 -port 22222

Launch the device Python application: the UDP client.

cd lab-schc-examples/at-modem/udp-client/
python3 -m device --template device/compression_rules.bin \
 --dev-eui fe:ff:ff:ff:fd:ff:00:00 --app-eui 00:00:00:00:00:00:00:00 \
 --app-key 11:11:11:11:11:11:11:11:11:11:11:11:11:11:11:11 \
 --ipv6-dev-prefix 5454:0000:0000:0000 --ipv6-dev-iid 0000:0000:0000:0002 \
 --ipv6-app-prefix abcd:0000:0000:0000 --ipv6-app-iid 0000:0000:0000:0001 \
 --ipv6-dev-port 33333 --ipv6-app-port 22222

If the program shows an error when opening the serial port, or you have multiple devices connected, edit the device/serial_device.py file and set the SERIAL_DEVICE parameter to the correct value.

Observe the terminal output as the UDP Client application communicates with the device through AT Commands:
1. First, it will configure the device and instruct it to join the network.
request : ATZ request : AT+SCHC=VERSION response : AT+SCHC=VERSION response : 3.0.0 response : OK request : ATE=0 response : ATE=0 response : OK request : AT+DEUI=fe:ff:ff:ff:fd:ff:00:00 response : OK request : AT+APPEUI=00:00:00:00:00:00:00:00 response : OK request : AT+APPKEY=11:11:11:11:11:11:11:11:11:11:11:11:11:11:11:11 response : OK request : AT+JOIN=C response : OK response : +JOINED
1. Then, the SCHC compression rule is loaded.
request : AT+SCHC=TPL,SET,b1008418960186010101010101818302181c8e880c040102000081410602880d080101000081410002880e140101000081440001234502880f100101000081420000028810080101000081411102881108010100008141400288121840010200008100028813184001020000810102881418400102000081020288151840010200008103028816100102000081040288171001020000810502881818100101000081420000028818191001010000814200000224b2 response : OK request : AT+SCHC=TPLPARAMS,SET,0,5454000000000000 response : OK request : AT+SCHC=TPLPARAMS,SET,1,0000000000000002 response : OK request : AT+SCHC=TPLPARAMS,SET,2,abcd000000000000 response : OK request : AT+SCHC=TPLPARAMS,SET,3,0000000000000001 response : OK request : AT+SCHC=TPLPARAMS,SET,4,8235 response : OK request : AT+SCHC=TPLPARAMS,SET,5,56ce response : OK
1. After that, the UDP Client program instructs the device to use the Datagram interface to set up the communication socket.
request : AT+SCHC=API,D response : OK request : AT+SCHC=SOCKET response : 0 response : OK request : AT+SCHC=BIND,0,5454:0000:0000:0000:0000:0000:0000:0002,33333 response : OK
1. Finally, the device and UDP Server Application exchange IP packets.
  - On the device:
  request : AT+SCHC=SEND,0,ABCD:0000:0000:0000:0000:0000:0000:0001,22222,ZRQXKRGGYUUMOXSSEYEOMHJNQOSARIWFKWVUTYYAMGTYLMVHAZLIAADCIDRNONIE response : OK response : +SENDOK,0 response : +RECVOK,0:5A5251584B5247475955554D4F5853534559454F4D484A4E514F5341524957464B575655545959414D4754594C4D5648415A4C49414144434944524E4F4E4945
  - On de application side:
  starting udp server on [abcd::1]:22222 receive uplink packet from the device [5454::2]:33333 b'ZRQXKRGGYUUMOXSSEYEOMHJNQOSARIWFKWVUTYYAMGTYLMVHAZLIAADCIDRNONIE' send downlink packet to the device [5454::2]:33333 b'ZRQXKRGGYUUMOXSSEYEOMHJNQOSARIWFKWVUTYYAMGTYLMVHAZLIAADCIDRNONIE'