ESP32 WiFiClientSecure Library – flush

/*
 * Author: Avant Maker
 * Date: February 24, 2025
 * Version: 1.0
 *
 * Description: This example demostrate how to use 
 * ESP32 WiFiClientSecure Libary's 
 * flush method to ensures that any buffered data in the
 * outgoing secure stream (e.g., an HTTPS connection)
 * is fully transmitted before proceeding
 * 
 * ATTENTION: The Root CA certificate has an expiration date. 
 * If the code fails to execute, it may be due to the Root CA
 * certificate has expired. Try obtaining the latest 
 * Root CA certificate and replacing the expired one in this code.
 * For detailed instructions on acquiring a website's
 * Root CA certificate, check out the link below:
 *
 * https://avantmaker.com/references/esp32-arduino-core-index/esp32-wificlientsecure-library/how-to-acquire-the-root-ca-certificate/
 *
 * 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>
#include <NetworkClientSecure.h>

const char* ssid = "your-SSID";          // Replace with your Wi-Fi SSID
const char* password = "your-PASSWORD";  // Replace with your Wi-Fi password
const char* host = "www.httpbin.org";
const int port = 443;

// Root CA certificate for www.httpbin.org (update with your server's CA if different)
const char* rootCACert = R"literal(
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
)literal";

// Optional: Add client certificate and key for mutual TLS if needed
// const char* clientCertKey = "";
// const char* clientCert = "";

NetworkClientSecure secureClient;

void setup() {
    Serial.begin(115200);
    
    // Connect WiFi
    WiFi.begin(ssid, password);
    while (WiFi.status() != WL_CONNECTED) {
        delay(500);
        Serial.print(".");
    }
    Serial.println("Connected to WiFi");

    // Set the Root CA Cert
    secureClient.setCACert(rootCACert);

    // Establish secure connection to server
    if (secureClient.connect(host, port)) {
        Serial.println("Connected to server");

        // Create the POST data
        String postData = "AvantMaker=HelloFromESP32";

        // Send the POST request
        secureClient.print("POST /post HTTP/1.1\r\n");
        secureClient.print("Host: www.httpbin.org\r\n");
        secureClient.print("Content-Type: application/x-www-form-urlencoded\r\n");
        secureClient.print("Content-Length: ");
        secureClient.print(postData.length());
        secureClient.print("\r\nConnection: close\r\n\r\n");
        secureClient.print(postData);

        // Flush the output buffer to ensure data is sent
        secureClient.flush();
        Serial.println("Request sent and flushed");

        // Wait for server response
        while (secureClient.connected() && !secureClient.available()) {
            delay(10);
        }

        // Read response
        if (secureClient.available()) {
            int lineNumber = 0;
            Serial.println("Server response:");
            while (secureClient.available()) {
                Serial.print("Line ");
                lineNumber++;
                Serial.print(lineNumber);
                Serial.print(" - ");
                String line = secureClient.readStringUntil('\n');
                Serial.println(line);
            }
        } else {
            Serial.println("No data available");
        }

        secureClient.stop();

    } else {
        Serial.println("Failed to connect to server! Check the code description for solution.");
        return;
    }     
}

void loop() {
}