IOT2: Reading IP address of the WiFi

On the networking level, IP devices are identified by MAC. In the case of our laboratory and network, you will obtain the IP address from the DHCP server integrated with the WiFi access point. To connect to the WiFi network, one needs to use credentials that are present in the general laboratory description, available here:

In this scenario, you will learn how to set up your device in STA (client to the AP) mode, connect to the AP, and read the obtained IP address. This scenario does not contain a UI part; it is up to the developer to implement it using one of the scenarios presented below.

To implement this scenario, it is necessary to get familiar with at least one of the following scenarios first:

• EMB5: Using LCD Display,
• EMB6: Using ePaper display,
• EMB7: Using OLED display.

A WiFi library is already included in the Arduino framework for ESP32, so there is no need to add it to the platformio.ini explicitly.

• C/C++ Language Embedded Programming Fundamentals,
• ESP32 General Information,
• SUT ESP32 Laboratory Node Hardware Reference,
• Networking for Espressif.

Connect to the “internal IoT” WiFI access point. Present the obtained IP address on the selected display. Handle critical situations such as no access and present an appropriate message on the screen (e.g., an error message). The steps below present only the reading part, not a display. Handling a display is presented in the EMBx scenarios, as listed above.

Check if you can clearly see a full display (of your choice) in your video stream. Book a device and create a dummy Arduino file with void setup()… and void loop()….

Include the WiFi management library in your source code:

#include <WiFi.h>

The WiFi library automatically initialises a singleton class, WiFi, which you can use to set up working mode, read MAC and IP, and perform many other operations.

Declare some constants, including AP SSID and passphrase and a variable to store IP:

const char* ssid = "REPLACE_WITH_CORRECT_SSID";
const char* pass = "REPLACE_WITH_CORRENT_PASSPHRASE";
IPAddress localIP;

Both ssid and pass are to be obtained from the hardware reference, available here: SUT ESP32 Laboratory Node Hardware Reference.

Set your device in the STA mode and connect to the WiFi AP:

  WiFi.mode(WIFI_STA);
  WiFi.begin(ssid, pass);
  while (WiFi.status() != WL_CONNECTED) {
    //Drop some info on display about connecting
    delay(1000);
  }

The WiFi.begin(…) returns the following statuses (value, enumerator: meaning):

• 0, WL_IDLE_STATUS: temporary status assigned when WiFi.begin() is called
• 1, WL_NO_SSID_AVAIL: when no SSID are available
• 2, WL_SCAN_COMPLETED: scan networks is completed
• 3, WL_CONNECTED: when connected to a WiFi network
• 4, WL_CONNECT_FAILED: when the connection fails for all the attempts
• 5, WL_CONNECTION_LOST: when the connection is lost
• 6, WL_DISCONNECTED: when disconnected from a network

Reading the IP as a String is as easy as simply calling:

   localIP = WiFi.localIP();

The IPAddress class contains the toString() method which formats the IP and returns in standard, dot-separated, four-octet text format.

Explicitly disconnect from the WiFi AP to free resources:

  WiFi.disconnect();  

Some useful WiFi functions are listed below:

• WiFi.reconnect() - reconnects the connection that was dropped, note it uses ssid and pass previously specified in the WiFi.begin(…), here you do not provide one.
• WiFi.RSSI() - once connected, you can get signal strength as int8_t integer.
• WiFi.setHostname(const char * hostname) - set host name for the ESP32 chip. Remember to use this function before connecting to the AP.

You should be able to connect to the WiFi and present the dynamically assigned IP address by the DHCP server.

I set a hostname, but it does appear on the router level.: There are many possible reasons; one is an active registration in the router (AP) that keeps an old IP address, so you need to wait until it expires; another reason is you have changed the hostname when you were connected to the AP.
Can I use a manually configured IP?: Actually, you can, but we strongly discourage it. You may accidentally overlap this IP address with some other device, router, or infrastructure, blocking its operation.

Project information

This Intellectual Output was implemented under the Erasmus+ KA2.
Project IOT-OPEN.EU Reloaded – Education-based strengthening of the European universities, companies and labour force in the global IoT market.
Project number: 2022-1-PL01-KA220-HED-000085090.

Erasmus+ Disclaimer
This project has been funded with support from the European Commission.
This publication reflects the views of only the author, and the Commission cannot be held responsible for any use that may be made of the information contained therein.

Copyright Notice
This content was created by the IOT-OPEN.EU Reloaded consortium, 2022,2024.
The content is Copyrighted and distributed under CC BY-NC Creative Commons Licence, free for Non-Commercial use.