.. _sockets-echo-server-sample:
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 :ref:`echo-server-sample`. 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:
:file:`samples/net/sockets/echo_server`.
Requirements
************
- :ref:`networking_with_qemu`
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 :ref:`networking_with_qemu`.
Build echo-server sample application like this:
.. zephyr-app-commands::
:zephyr-app: samples/net/sockets/echo_server
:board: <board_to_use>
:goals: build
:compact:
``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 :ref:`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:
.. zephyr-app-commands::
:zephyr-app: samples/net/sockets/echo_server
:board: qemu_x86
:conf: "prj.conf overlay-tls.conf"
:goals: build
:compact:
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
:ref:`sockets-echo-client-sample` 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 :ref:`networking_with_qemu` guide.
Run echo-server application in QEMU:
.. zephyr-app-commands::
:zephyr-app: samples/net/sockets/echo_server
:host-os: unix
:board: qemu_x86
:goals: run
:compact:
In a terminal window:
.. code-block:: console
$ 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 :ref:`sockets-echo-client-sample` documentation for an alternate
way of running, with the echo-server on the Linux host and the echo-client
in QEMU.
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