Telnet console

.. zephyr:code-sample:: telnet-console
   :name: Telnet console
   :relevant-api: shell_api net_core net_if net_mgmt

   Access Zephyr shell over telnet.

Overview
********

This application will setup IPv4/IPv6 addresses on the default
network interface. The telnet console service is started transparently
by the kernel, along with the shell and two shell modules: net and kernel.
Once up and running, you can connect to the target over the network,
using a telnet client.

Requirements
************

- :ref:`networking_with_qemu`


Building and Running
********************

QEMU x86
========

These are instructions for how to use this sample application using
QEMU on a Linux host connected to a network with DHCP service.

To use QEMU for testing, follow the :ref:`networking_with_qemu` guide.

Run Zephyr samples/net/telnet application in QEMU:

.. zephyr-app-commands::
   :zephyr-app: samples/net/telnet
   :host-os: unix
   :board: qemu_x86
   :goals: run
   :compact:

Once started, you should see you IP address details for example:

.. code-block:: console

    [Setup] [INF] main: Starting Telnet sample
    [Setup] [INF] setup_ipv4: IPv4 address: 192.0.2.1
    [Setup] [INF] setup_ipv6: IPv6 address: 2001:db8::1

At this point, your QEMU guest is up and running. Connect to the telnet
console from your linux host this way:

.. code-block:: console

    $ telnet 192.0.2.1
    Telnet escape character is '^]'.
    Trying 192.0.2.1...
    Connected to 192.0.2.1.
    Escape character is '^]'.

Now type enter, the shell prompt will appear and you can enter commands,
for example ``help``.


Freedom-K64F Board
===================

These are instructions for how to use this sample application running on a
Freedom-K64F board. Unlike running it on QEMU, :ref:`Freedom-K64F board
<frdm_k64f>` network configuration for IPv4 will rely on DHCPv4. You cad modify
the :file:`prj_frdm_k64f.conf` to set static IPv4 addresses if it is really needed.

For detailed instructions about building, flashing and using the serial console
logs, follow the  :ref:`Freedom-K64F board <frdm_k64f>` documentation section.

Connect ethernet cable from :ref:`Freedom-K64F <frdm_k64f>` board to a
local network providing IPv4 address configuration via DHCPv4. Creating your own
DHCP server on a local network is not in the scope of this README.

Build Zephyr samples/net/telnet application:

.. zephyr-app-commands::
   :zephyr-app: samples/net/telnet
   :board: frdm_k64f
   :goals: build
   :compact:

Flash the resulting Zephyr binary following the :ref:`Freedom-K64F <frdm_k64f>`
board documentation noted above.

From your host computer, open a serial console to your board:

.. code-block:: console

    $ sudo screen /dev/ttyACM0 115200

Plug the Ethernet cable to the :ref:`Freedom-K64F <frdm_k64f>` board.
Reset the board, you should see first on the console:

.. code-block:: console

    [dev/eth_mcux] [INF] eth_0_init: Enabled 100M full-duplex mode.
    [dev/eth_mcux] [DBG] eth_0_init: MAC 00:04:9f:69:c7:36
    shell> [Setup] [INF] main: Starting Telnet sample
    [Setup] [INF] setup_dhcpv4: Running dhcpv4 client...
    [Setup] [INF] setup_ipv6: IPv6 address: 2001:db8::1

And if the DHCPv4 client succeeds, you will soon see something like:

.. code-block:: console

   [Setup] [INF] ipv4_addr_add_handler: IPv4 address: 192.168.0.21
   [Setup] [INF] ipv4_addr_add_handler: Lease time: 86400 seconds
   [Setup] [INF] ipv4_addr_add_handler: Subnet: 255.255.255.0
   [Setup] [INF] ipv4_addr_add_handler: Router: 192.168.0.1

The above result depends on your local network.
At this point you should be able to connect via telnet over the network.
On your linux host:

.. code-block:: console

    $ telnet 192.168.0.21
    Telnet escape character is '^]'.
    Trying 192.168.0.21...
    Connected to 192.168.0.1.
    Escape character is '^]'.

You are now connected, and as for the UART console, you can type in
your commands and get the output through your telnet client.