Socket Echo Server

Overview

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.

This sample is a port of the Echo Server. It has been rewritten to use socket API instead of native net-app API.

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

Requirements

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.

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> ..
ninja

board_to_use defaults to qemu_x86. In this case, you can run the application in QEMU using make run. If you used another BOARD, you will need to consult its documentation for application deployment instructions. You can read about Zephyr support for specific boards in the documentation at Supported Boards.

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 -DOVERLAY_CONFIG=overlay-tls.conf when running cmake.

The certificate used by the sample can be found in the sample’s src 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.