Socket Echo Server¶
The echo-server sample application for Zephyr implements a UDP/TCP server that complements the echo-client sample application: the echo-server listens for incoming IPv4 or IPv6 packets (sent by the echo client) and simply sends them back.
The source code for this sample application can be found at: samples/net/sockets/echo_server.
Building and Running¶
There are multiple ways to use this application. One of the most common usage scenario is to run echo-server application inside QEMU. This is described in Networking with QEMU.
There are configuration files for different boards and setups in the echo-server directory:
prj.confGeneric config file, normally you should use this.
overlay-ot.confThis overlay config enables support for OpenThread.
overlay-802154.confThis 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-bt.confThis overlay config enables support for Bluetooth IPSP connectivity.
overlay-qemu_802154.confThis overlay config enables support for two QEMU’s when simulating IEEE 802.15.4 network that are connected together.
overlay-tls.confThis overlay config enables support for TLS.
Build echo-server sample application like this:
# On Linux/macOS cd $ZEPHYR_BASE/samples/net/sockets/echo_server mkdir build && cd build # On Windows cd %ZEPHYR_BASE%\samples\net\sockets\echo_server mkdir build & cd build cmake -GNinja -DBOARD=<board to use> -DCONF_FILE=<config file to use> .. ninja
Example building for the nRF52840_pca10056 with OpenThread support:
cd $ZEPHYR_BASE/samples/net/sockets/echo_server mkdir build && cd build cmake -GNinja -DBOARD=nrf52840_pca10056 -DCONF_FILE="prj.conf overlay-ot.conf" .. ninja run
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:
# On Linux/macOS cd $ZEPHYR_BASE/samples/net/sockets/echo_server mkdir build && cd build # On Windows cd %ZEPHYR_BASE%\samples\net\sockets\echo_server mkdir build & cd build cmake -GNinja -DBOARD=qemu_x86 -DCONF_FILE="prj.conf overlay-tls.conf" .. ninja
An alternative way is to specify
The certificate used by the sample can be found in the sample’s
directory. The default certificates used by Socket Echo Server and
Socket Echo Client enable establishing a secure connection
between the samples.
Running echo-client in Linux Host¶
There is one useful testing scenario that can be used with Linux host. Here echo-server is run in QEMU and echo-client is run in Linux host.
To use QEMU for testing, follow the Networking with QEMU guide.
Run echo-server application in QEMU:
cd $ZEPHYR_BASE/samples/net/sockets/echo_server mkdir build && cd build cmake -GNinja -DBOARD=qemu_x86 .. ninja run
In a terminal window:
$ sudo ./echo-client -i tap0 2001:db8::1
Note that echo-server must be running in QEMU before you start the echo-client application in host terminal window.
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 Socket Echo Client documentation for an alternate way of running, with the echo-server on the Linux host and the echo-client in QEMU.