Echo client (advanced)

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Overview

The echo-client sample application for Zephyr implements a UDP/TCP client that will send IPv4 or IPv6 packets, wait for the data to be sent back, and then verify it matches the data that was sent.

The source code for this sample application can be found at: samples/net/sockets/echo_client.

Requirements

Building and Running

There are multiple ways to use this application. One of the most common usage scenario is to run echo-client application inside QEMU. This is described in Networking with QEMU.

There are configuration files for different boards and setups in the echo-client directory:

  • prj.conf Generic config file, normally you should use this.

  • overlay-ot.conf This overlay config enables support for OpenThread.

  • overlay-802154.conf This overlay config enables support for native IEEE 802.15.4 connectivity. Note, that by default IEEE 802.15.4 L2 uses unacknowledged communication. To improve connection reliability, acknowledgments can be enabled with shell command: ieee802154 ack set.

  • overlay-qemu_802154.conf This overlay config enables support for two QEMU’s when simulating IEEE 802.15.4 network that are connected together.

  • overlay-tls.conf This overlay config enables support for TLS.

Build echo-client sample application like this:

west build -b <board to use> samples/net/sockets/echo_client -- -DCONF_FILE=<config file to use>

Example building for the nrf52840dk/nrf52840 with OpenThread support:

west build -b nrf52840dk/nrf52840 samples/net/sockets/echo_client -- -DCONF_FILE="prj.conf overlay-ot.conf"
west build -t run

Example building for the IEEE 802.15.4 RF2XX transceiver:

west build -b [samr21_xpro | sam4s_xplained | sam_v71_xult/samv71q21] samples/net/sockets/echo_client -- -DEXTRA_CONF_FILE=overlay-802154.conf
west flash

In a terminal window you can check if communication is happen:

$ minicom -D /dev/ttyACM1

Enabling TLS support

Enable TLS support in the sample by building the project with the overlay-tls.conf overlay file enabled, for example, using these commands:

west build -b qemu_x86 samples/net/sockets/echo_client -- -DCONF_FILE="prj.conf overlay-tls.conf"

An alternative way is to specify -DEXTRA_CONF_FILE=overlay-tls.conf when running west build or cmake.

The certificate and private key used by the sample can be found in the sample’s src directory. The default certificates used by Socket Echo Client and Echo server (advanced) enable establishing a secure connection between the samples.

SOCKS5 proxy support

It is also possible to connect to the echo-server through a SOCKS5 proxy. To enable it, use -DEXTRA_CONF_FILE=overlay-socks5.conf when running west build or cmake.

By default, to make the testing easier, the proxy is expected to run on the same host as the echo-server in Linux host.

To start a proxy server, for example a builtin SOCKS server support in ssh can be used (-D option). Use the following command to run it on your host with the default port:

For IPv4 proxy server:

$ ssh -N -D 0.0.0.0:1080 localhost

For IPv6 proxy server:

$ ssh -N -D [::]:1080 localhost

Run both commands if you are testing IPv4 and IPv6.

To connect to a proxy server that is not running under the same IP as the echo-server or uses a different port number, modify the following values in echo_client/src/tcp.c.

#define SOCKS5_PROXY_V4_ADDR IPV4_ADDR
#define SOCKS5_PROXY_V6_ADDR IPV6_ADDR
#define SOCKS5_PROXY_PORT    1080

Running echo-server in Linux Host

There is one useful testing scenario that can be used with Linux host. Here echo-client is run in QEMU and echo-server is run in Linux host.

To use QEMU for testing, follow the Networking with QEMU guide.

In a terminal window:

$ sudo ./echo-server -i tap0

Run echo-client application in QEMU:

west build -b qemu_x86 samples/net/sockets/echo_client -- -DCONF_FILE="prj.conf overlay-linux.conf"
west build -t run

Note that echo-server must be running in the Linux host terminal window before you start the echo-client application in QEMU. Exit QEMU by pressing CTRL+A x.

You can verify TLS communication with a Linux host as well. See https://github.com/zephyrproject-rtos/net-tools documentation for information on how to test TLS with Linux host samples.

See the Echo server (advanced) documentation for an alternate way of running, with the echo-client on the Linux host and the echo-server in QEMU.

OpenThread RCP+Zephyr HOST (SPINEL connection via UART)

Prerequisites:

$ make echo-server

  • Program nRF RCP from Nordic nrf SDK (v2.7.0):

(v2.7.0) ~/ncs$ west build -p always -b nrf21540dk/nrf52840 -S logging nrf/samples/openthread/coprocessor

  • Build mimxrt1020_evk HOST (Zephyr):

west build -b mimxrt1020_evk samples/net/sockets/echo_client -- -DCONF_FILE="prj.conf overlay-ot-rcp-host-uart.conf"

And flash

$ west flash -r pyocd -i 0226000047784e4500439004d9170013e56100009796990

  • Connect the nRF RCP with IMXRT1020 (HOST) via UART

/*
 * imxrt1020_evk -> HOST
 * nRF21540-DK   -> RCP (nrf/samples/openthread/coprocessor)
 * LPUART2 used for communication:
 *  nRF21540 (P6) P0.08 RXD -> IMXRT1020-EVK (J17) D1 (GPIO B1 08) (TXD)
 *  nRF21540 (P6) P0.07 CTS -> IMXRT1020-EVK (J19) D8 (GPIO B1 07) (RTS)
 *  nRF21540 (P6) P0.06 TXD -> IMXRT1020-EVK (J17) D0 (GPIO B1 09) (RXD)
 *  nRF21540 (P6) P0.05 RTS -> IMXRT1020-EVK (J17) D7 (GPIO B1 06) (CTS)
 */

Most notable ones:

  1. Create otbr0 network bridge to have access to OT network from HOST Linux PC

sudo docker network create --ipv6 --subnet fd11:db8:1::/64 -o com.docker.network.bridge.name=otbr0 otbr

  1. Pull docker container for OTBR:

docker pull nrfconnect/otbr:84c6aff

  1. Start the docker image:

sudo modprobe ip6table_filter
sudo docker run -it --rm --privileged --name otbr --network otbr -p 8080:80 --sysctl "net.ipv6.conf.all.disable_ipv6=0 net.ipv4.conf.all.forwarding=1 net.ipv6.conf.all.forwarding=1" --volume /dev/ttyACM5:/dev/radio nrfconnect/otbr:84c6aff --radio-url spinel+hdlc+uart:///dev/radio?uart-baudrate=1000000

  1. Add proper routing (fd11:22::/64 are the IPv6 addresses - On-Mesh - which allow accessing the OT devices) on HOST PC (x86_64)

sudo ip -6 route add fd11:22::/64 dev otbr0 via fd11:db8:1::2

And the output for on-OT address:

ip route get fd11:22:0:0:5188:1678:d0c0:6893
fd11:22::5188:1678:d0c0:6893 from :: via fd11:db8:1::2 dev otbr0 src fd11:db8:1::1 metric 1024 pref medium

  1. Start the console to the docker image:

sudo docker exec -it otbr /bin/bash

Test with e.g.

ot-ctl router table
ot-ctl ipaddr

Configure OTBR

On the HOST PC’s webbrowser: http://localhost:8080/

Go to Form and leave default values - e.g:

  • Network Key: 00112233445566778899aabbccddeeff

  • On-Mesh Prefix: fd11:22::

  • Channel: 15

to “FORM” the OT network.

Note: The “On-Mesh Prefix” shall match the one setup in otbr0 routing.

Configure RCP (nRF21540-DK) + OT HOST (mimxrt1020)

ot factoryreset
ot dataset networkkey 00112233445566778899aabbccddeeff
ot ifconfig up

In the HOST PC www webpage interface please: Commission -> Joiner PSKd* set to J01NME -> START COMMISSION

ot joiner start J01NME
ot thread start

The ot ipaddr shall show IPv6 address starting from fd11:22:0:0:. This one can be accessed from HOST’s PC network (via e.g. ping -6 fd11:22:0:0:e8bf:266b:63ca:eff4).

Start echo-server on HOST PC (x86-64)

./echo-server -i otbr0

See also

BSD Sockets compatible API
TLS credentials management