Wireless Communication

Work Process Detail

1️⃣ Connect two ESP32 boards to your computer.

2️⃣ Open Arduino IDE with ESP32 board definitions installed.

3️⃣ On the Server ESP32 (acts as Wi-Fi Access Point + TCP Server), upload the Server Code.

🟢 ESP32 #1 → WiFi Access Point + TCP Server

#include <WiFi.h>

WiFiServer server(80);  // TCP server on port 80

void setup() {
  Serial.begin(115200);
  WiFi.softAP("ESP32_SERVER", "12345678"); // AP SSID & Password
  Serial.println("Access Point Started");
  server.begin();
}

void loop() {
  WiFiClient client = server.available();
  if (client) {
    Serial.println("Client Connected");
    while (client.connected()) {
      if (client.available()) {
        String data = client.readStringUntil('\n');
        Serial.print("Received: ");
        Serial.println(data);
      }
    }
    client.stop();
    Serial.println("Client Disconnected");
  }
}

This ESP32 creates a Wi-Fi network (like a mini router) and waits for the other ESP32 to send messages.

📝 Line by line explanation

#include <WiFi.h>

👉 Add the Wi-Fi library so ESP32 knows how to work with Wi-Fi.

WiFiServer server(80);

👉 Tell ESP32 to listen for connections on port 80 (just a standard communication port).

void setup() {

👉 Setup runs once when you turn on the board.

Serial.begin(115200);

👉 Open communication with your computer, so you can see messages in Serial Monitor.

WiFi.softAP("ESP32_SERVER", "12345678");

👉 Start a Wi-Fi network called ESP32_SERVER. Password is 12345678.

(This is the Wi-Fi your client will connect to.)

server.begin();

👉 Start waiting for devices (clients) to connect.

void loop() {

👉 This runs over and over forever.

WiFiClient client = server.available();

👉 Check if another ESP32 (a client) is trying to connect.

if (client) {

👉 If someone connects:

while (client.connected()) {

👉 While that device is still connected:

if (client.available()) {

👉 If the client sends any message:

String data = client.readStringUntil('\n');

👉 Read the message and save it in data.

Serial.println(data);

👉 Print the message on the computer screen (in Serial Monitor).

client.stop();

👉 When client finishes, disconnect.

✅ What it does:

• It makes a Wi-Fi network.

• It waits for the client ESP32 to connect.

• It reads messages sent from the client and prints them.

4️⃣ On the Client ESP32 (connects to AP + sends data), upload the Client Code.

🟢 ESP32 #2 → WiFi Station + TCP Client

#include <WiFi.h>

const char* ssid = "ESP32_SERVER";
const char* password = "12345678";

WiFiClient client;

void setup() {
  Serial.begin(115200);
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("\nConnected to Server");
  client.connect("192.168.4.1", 80);   // ESP32 AP IP address
}

void loop() {
  if (client.connected()) {
    client.println("Hello from CLIENT");
    Serial.println("Message Sent");
    delay(2000);
  }
}

This ESP32 connects to the server’s Wi-Fi and sends a message every 2 seconds.

📝 Line by line explanation

#include <WiFi.h>

👉 Add Wi-Fi capability.

const char* ssid = "ESP32_SERVER";
const char* password = "12345678";

👉 These must match the server Wi-Fi name & password.

WiFiClient client;

👉 Create a client object (a device that connects to a server).

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

👉 Open communication with your computer (Serial Monitor).

WiFi.begin(ssid, password);

👉 Connect to server’s Wi-Fi.

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

👉 Wait here until Wi-Fi connection is successful.

👉 Print dots (.) while waiting.

client.connect("192.168.4.1", 80);

👉 After Wi-Fi connects, talk to the Server ESP32.

👉 192.168.4.1 = always the IP of the ESP32 server.

void loop() {

👉 This part repeats forever.

if (client.connected()) {
client.println("Hello from CLIENT");

👉 If connection is good → send the message “Hello from CLIENT” to Server.

Serial.println("Message Sent");

👉 Tell you that the message was sent.

delay(2000);

👉 Wait 2 seconds and repeat.

✅ What it does:

• It connects to the ESP32 server Wi-Fi.

• Every 2 seconds, it sends “Hello from CLIENT”.

• The Server ESP32 prints that message.

5️⃣ Open Serial Monitors on both boards and watch the communication!