ESP32 WiFiClient Library – readString

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Description

The readString method of the ESP32’s WiFiClient library reads all available characters from the server and returns them as a String object. This is particularly useful for handling server responses where the length of the incoming data is unknown or when you want to process the entire response at once.


Syntax and Usage

The readString method is used as follows:

String response = client.readString();

Here, client is an instance of WiFiClient. The method does not take any arguments and returns the data as a String.

For practical applications and examples of this method, please consult the “Example Code” section on this page. This section provides comprehensive guidance to help you better understand and apply the method effectively.


Argument(s)

This method does not require any arguments.


Return Value

The readString method returns a String containing all the characters read from the server. If no data is available, it returns an empty String.


Example Codes

Below is an example demonstrating how to use the readString method to read the entire response from a server:

Example: Reading Server Response

This example connects to www.httpbin.org and sends a simple HTTP GET request. It then reads the server’s response using the readString method and prints it to the Serial Monitor.

/*
 * Author: Avant Maker
 * Date: February 24, 2025
 * Version: 1.0
 * Description: This example demonstrates how to use 
 * ESP32 WiFiClient Library's readString method to
 * read the entire response from a server.
 *
 * License: MIT 
 * 
 * Code Source: This example code is sourced from the Comprehensive 
 * Guide to the ESP32 Arduino Core Library, accessible on 
 * AvantMaker.com. For additional code examples and in-depth 
 * documentation related to the ESP32 Arduino Core Library, 
 * please visit:
 *
 * https://avantmaker.com/references/esp32-arduino-core-index/
 *
 * AvantMaker.com, your premier destination for all things 
 * DIY, AI, IoT, Smart Home, and STEM projects. We are dedicated 
 * to empowering makers, learners, and enthusiasts with the resources
 * they need to bring their innovative ideas to life.
 */

#include <WiFi.h>

const char* ssid     = "your-ssid";      // Replace with your WiFi SSID
const char* password = "your-password";  // Replace with your WiFi password

void setup() {
    Serial.begin(115200);
    delay(1000);

    // Connect to Wi-Fi
    Serial.print("Connecting to ");
    Serial.println(ssid);
    WiFi.begin(ssid, password);

    while (WiFi.status() != WL_CONNECTED) {
        delay(500);
        Serial.print(".");
    }
    Serial.println("\nConnected to WiFi");
}

void loop() {
    WiFiClient client;
    const char* host = "www.httpbin.org";
    const int httpPort = 80;

    if (!client.connect(host, httpPort)) {
        Serial.println("Connection failed");
        return;
    }

    // Send HTTP GET request
    client.print(String("GET /get HTTP/1.1\r\n") +
                 "Host: " + host + "\r\n" +
                 "Connection: close\r\n\r\n");

    // Wait for server response
    while (client.connected() && !client.available()) {
        delay(1);
    }

    // Read the response
    String response = client.readString();
    Serial.println("Server response:");
    Serial.println(response);

    // Close the connection
    client.stop();

    // Wait before the next request
    delay(10000);
}

In this example:

  • The ESP32 connects to the specified Wi-Fi network.
  • It establishes a connection to www.httpbin.org on port 80.
  • An HTTP GET request is sent to the server.
  • The response from the server is read using client.readString() and printed to the Serial Monitor.
  • The connection is then closed, and the device waits for 10 seconds before repeating the process.

ESP32 Library Index

ESP32 Arduino Core Library


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