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Azure Sphere – DHCP client

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This sample application demonstrates how to renew or release the current IP address that the network's DHCP server has assigned to the MT3620 device.

The sample configures the desired network interface to be targeted, either Wi-Fi or Ethernet, according to the configuration in the application's global variable. Buttons A and B are used to respectively Release and Renew the current IP address, while the color of the status LED will always indicate the network interface's status from the OS.

The sample uses the following Azure Sphere libraries.

Library Purpose
eventloop Invokes handlers for timer events.
gpio Manages button A (SAMPLE_BUTTON_1), Manages button B (SAMPLE_BUTTON_2) and LED 2 tri-channel on the device.
log Displays messages in the Device Output window during debugging.
networking Manages the network configuration of the device.

Contents

File/folder Description
app_manifest.json Application manifest file, which describes the resources.
CMakeLists.txt CMake configuration file, which contains the project information and is required for all builds.
CMakePresets.json CMake presets file, which contains the information to configure the CMake project.
launch.vs.json JSON file that tells Visual Studio how to deploy and debug the application.
LICENSE.txt The license for this sample application.
main.c Main C source code file.
README.md This README file.
.vscode Folder containing the JSON files that configure Visual Studio Code for deploying and debugging the application.
HardwareDefinitions Folder containing the hardware definition files for various Azure Sphere boards.

Prerequisites

The sample requires the following hardware:

  • An Azure Sphere development board that supports the Sample Appliance hardware requirements.

    Note: By default, the sample targets the Reference Development Board design, which is implemented by the Seeed Studios MT3620 Development Board. To build the sample for different Azure Sphere hardware, change the value of the TARGET_HARDWARE variable in the CMakeLists.txt file. For detailed instructions, see the Hardware Definitions README file.

  • The development board must be updated to Azure Sphere OS version 24.03 or above.

Setup

Complete the following steps to set up this sample:

  1. Ensure that your Azure Sphere device is connected to your computer, and your computer is connected to the internet.

  2. Ensure that you have Azure Sphere SDK version 24.03 or above. At the command prompt, run az sphere show-sdk-version to check. Upgrade the Azure Sphere SDK for Windows or Linux as needed.

  3. Ensure that the Azure CLI is installed. At a minimum, the Azure CLI version must be 2.45.0 or later.

  4. Install the Azure Sphere extension.

  5. Enable application development, if you have not already done so, by entering the az sphere device enable-development command at the command prompt.

  6. Clone the Azure Sphere samples repository and find the DHCP_HighLevelApp sample in the DHCP folder or download the zip file from the Microsoft samples browser.

  7. Configure the sample application to work with the desired network interface. There are two different types of network interface configurations possible (see the network interface configuration section for setup instructions):

    • System default, MT3620's on-chip Wi-Fi ("wlan0").
    • External ethernet interface chip ("eth0").

    The sample can be configured with any one type at a time, before compiling and running it.

  8. Configure networking on your device. You must either set up WiFi or set up Ethernet on your development board, depending on the type of network connection you are using.

Network interface configuration

The default network interface is set to Wi-Fi, in the application's global variable currentNetInterface:

/// <summary>
///     Available network interface device names.
/// </summary>
#define NET_INTERFACE_WLAN     "wlan0"
#define NET_INTERFACE_ETHERNET "eth0"

// User configuration.
const char *const currentNetInterface = NET_INTERFACE_WLAN;

To switch to the Ethernet interface, simply assign the NET_INTERFACE_ETHERNET value to the currentNetInterface global variable, which can be found in main.c.

Build and run the sample

To build and run this sample, follow the instructions in Build a sample application.

Test the sample

When the sample runs, it loops until it successfully enables the configured network interface, according to your configuration in the application's global variable currentNetInterface, while disabling the other one available.

The output will be displayed in the terminal window, and it will show any transition in the current network interface's status, according to the statuses enumerated in the OS's Networking_InterfaceConnectionStatus enum type.

Here is an example of the output, using both 'wlan0' and 'eth0' interfaces:

Remote debugging from host 192.168.35.1, port 60337
INFO: DHCP High Level Application starting.
INFO: Successfully initiated peripherals.
INFO: Network interface 'wlan0' is connected to the Internet (local IP address [192.168.0.135]).
INFO: Successfully released the IP address.
INFO: Network interface 'wlan0' is connected to the network (no IP address assigned).
INFO: Successfully renewed the IP address.
INFO: Network interface 'wlan0' is connected and has been assigned IP address [192.168.0.135].
INFO: Network interface 'wlan0' is connected to the Internet (local IP address [192.168.0.135]).

Remote debugging from host 192.168.35.1, port 57127
INFO: DHCP High Level Application starting.
INFO: Successfully initiated peripherals.
ERROR: Network interface 'eth0' NOT ready!
INFO: Attempting to enable network interface 'eth0'.
INFO: Network interface is now set to 'eth0'.
INFO: Network interface 'eth0' is up but not connected to the network.
INFO: Network interface 'eth0' is connected to the network (no IP address assigned).
INFO: Network interface 'eth0' is connected and has been assigned IP address [192.168.0.135].
INFO: Network interface 'eth0' is connected to the Internet (local IP address [192.168.0.242]).
INFO: Successfully released the IP address.
INFO: Network interface 'eth0' is connected to the network (no IP address assigned).
INFO: Successfully renewed the IP address.
INFO: Network interface 'eth0' is connected to the Internet (local IP address [192.168.0.242]).

Note: as noticeable above, depending on the network setup/speed, some network interface state transitions may not appear in the output if they occur between the timer's interleaved checks..

  • Press Button A to release the current IP address assigned by the network's DHCP server.

    Note: by design, once the IP address is released, the network interface will not be automatically reassigned an IP address by the DHCP server, until the renew IP address is explicitly requested (i.e. by pressing Button B), or a device restart (or power-cycle) is performed.

  • Press Button B to renew the current IP address assigned by the network's DHCP server, or request one if previously released.

The color of the status LEDs indicates the following:

LED color State
Turned off The network interface is unavailable.
Red The network interface is up and available, but hasn't yet connected to the network.
Yellow (Red + Green) The network interface is up and connected to the network, but hasn't yet received an IP address from the network's DHCP server.
Blue The network interface is up, connected to the network and has successfully acquired an IP address from the network's DHCP server.
Green The network interface is fully operative and connected up to the Internet.

Next steps