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-ppp.confThis overlay config enables support for PPP (Point-to-Point Protocol).
overlay-tls.confThis overlay config enables support for TLS.
overlay-tunnel.confThis overlay config enables support for IP tunneling.
Build echo-server sample application like this:
west build -b <board to use> samples/net/sockets/echo_server -- -DCONF_FILE=<config file to use>
Example building for the nrf52840dk_nrf52840 with OpenThread support:
west build -b nrf52840dk_nrf52840 samples/net/sockets/echo_server -- -DCONF_FILE="prj.conf overlay-ot.conf" west build -t run
Example building for the atsamr21_xpro with RF2XX driver support:
west build -b [atsamr21_xpro | sam4e_xpro | sam_v71_xult] samples/net/sockets/echo_server -- -DOVERLAY_CONFIG=overlay-802154.conf west flash
In a terminal window you can check if communication is happen:
$ minicom -D /dev/ttyACM0
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_server -- -DCONF_FILE="prj.conf overlay-tls.conf"
An alternative way is to specify
west build or
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:
west build -b qemu_x86 samples/net/sockets/echo_server west build -t 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.