How to assign a fixed IP to an ESP32 ESP8266 or ESP01 project

20 October 2020
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3 minutes

When developing an object connected to WiFi with an ESP32, ESP8266 or ESP-01 (or any other microcontroller for that matter), it is much more practical to assign a fixed IP address. We can thus always connect to the object on the local network even in the event of a change of router or internet box.

By carrying out port routing, we can also connect from the Internet to our connected objects. However, beware of security vulnerabilities. It is better to connect your objects to a home automation server which is the job after all!

How to assign a fixed IP address to an ESP8266 or ESP-01 project?

The ESP8266WiFi library allows you to precisely assign the connection parameters:

IP IP address you want to assign
DNS DNS server, it is he who assigns the IP address. Here, we inform him that we want to reserve a fixed IP address. By default, we use the DNS server of the internet box or the router, so we indicate the same address.
GATEWAY This is the IP address of the internet box or router
SUBNET subnet. Generally, it is 255, 255, 255, 0. It will be necessary to check directly at the level of the internet box or the router

Here, we will assign the IP address 192.168.1.40 to the ESP01 or ESP8266 module.

IPAddress ip(192, 168, 1, 40);
IPAddress dns(192, 168, 1, 1);
IPAddress gateway(192, 168, 1, 1);
IPAddress subnet(255, 255, 255, 0);

The WiFi.config() method is used to configure the IP address and connection parameters to the local WiFi network.

WiFi.config(ip, dns, gateway, subnet);

Then we can connect as usual

WiFi.begin(ssid, password);

Read this article to learn more about the ESP8266WiFi library

How to assign a fixed IP address to an ESP project

The WiFi.h library for ESP32 is the equivalent of the ESP8266WiFi library.

The configuration and the call of the methods are perfectly identical!

You just have to include conditional code at the start of the project to load the library that corresponds to the platform. Detection is automatic.

#ifdef ESP32 
  #include <WiFi.h>
#else 
  #include <ESP8266WiFi.h> 
#endif

Upload the Arduino code to test the fixed IP address

Here is a complete code example that you can upload from the Arduino IDE or PlatformIO.

The code is ESP32 and ESP8266 compatible (including ESP01). On the Arduino IDE, you can remove the first line #include <Arduino.h>.

#include <Arduino.h>
#ifdef ESP32
  #include <WiFi.h>
#else
  #include <ESP8266WiFi.h>
#endif

const char* ssid = "enter_your_ssid";
const char* password = "enter_your_password";

WiFiServer server(80);

void setup() {

  Serial.begin(115200);
  delay(10);

  IPAddress ip(192, 168, 1, 40);
  IPAddress dns(192, 168, 1, 1);
  IPAddress gateway(192, 168, 1, 1);
  IPAddress subnet(255, 255, 255, 0);
  WiFi.config(ip, dns, gateway, subnet);

  WiFi.begin(ssid, password);
 
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print("...");
  }
  Serial.println("WiFi connected");

  server.begin();
  Serial.println("Web server running.");
  delay(500);

  Serial.println(WiFi.localIP());
}

void loop() {
  // put your main code here, to run repeatedly:
}

PlatformIO configurations for ESP32, ESP8266 or ESP-01

Here are some PlatformIO configurations for a LoLin d1 Mini (ESP8266), an ESP-01 (512KB) / ESP-01S (1MB) WiFi module or a LoLin D32 Pro (ESP32).

LoLin d1 mini (ESP8266) ESP-01 (512Ko) or ESP-01S (1Mo) LoLin D32 Pro (ESP32)

[env:d1_mini_lite]
platform = espressif8266
board = d1_mini_lite
framework = arduino
monitor_speed = 115200

[env:esp01_1m]
platform = espressif8266
board = esp01_1m
framework = arduino
;upload_protocol = esptool
;board_build.flash_mode = dout
;upload_speed = 115200
monitor_speed = 115200

[env:esp01]
platform = espressif8266
board = esp01
framework = arduino
;upload_protocol = esptool
;board_build.flash_mode = dout
;upload_speed = 115200
monitor_speed = 115200

[env:lolin_d32_pro]
platform = espressif32
board = lolin_d32_pro
framework = arduino
monitor_speed = 115200

Check the assigned IP address

Upload the project and open the serial monitor to verify that the IP address has been correctly assigned

From the Arduino IDE

From PlatformIO

--- More details at http://bit.ly/pio-monitor-filters
--- Miniterm on /dev/cu.usbserial-1410  115200,8,N,1 ---
--- Quit: Ctrl+C | Menu: Ctrl+T | Help: Ctrl+T followed by Ctrl+H ---
.....................WiFi connected
Web server running.
192.168.1.40