Using ESP32 Communication for a Multiplayer Pong Game Using WiFi (UDP)

Introduction

This guide will walk you through creating a multiplayer Pong game using two ESP32 boards. The boards communicate over Wi-Fi using UDP, chosen for its low latency, making it ideal for real-time applications like gaming. You’ll learn how to connect OLED displays, read input from buttons, and establish a communication protocol using UDP.

Components Required

To complete this project, you’ll need the following components:

2 x ESP32 Boards
2 x SH1106 OLED Displays (SSD1306 can also be used with a slight modification in the code)
4 x Push Buttons (2 for each board)
Jumper Wires
Breadboards
USB Cables

1. Hardware Setup

Connecting the OLED Displays

The SH1106 OLED displays will connect to the ESP32 boards via I2C. The wiring is as follows:

SDA (Data Line): Connect to ESP32 pin 21
SCL (Clock Line): Connect to ESP32 pin 22
VCC: Connect to 3.3V on ESP32
GND: Connect to GND on ESP32

Connecting the Push Buttons

Each ESP32 will have two buttons to control the paddles. Connect them as follows:

Button 1 (Up): Connect one leg to GPIO 2 and the other leg to GND.
Button 2 (Down): Connect one leg to GPIO 4 and the other leg to GND.

Note: You can use pull-up resistors or enable the internal pull-ups in the code to ensure stable button inputs.

2. Software Setup

Installing Required Libraries

Ensure the following libraries are installed in your Arduino IDE:

Adafruit_GFX: For graphics support on the OLED display.
Adafruit_SH1106: For interfacing with the SH1106 OLED display. (Use Adafruit_SSD1306 if you're using the SSD1306 display instead).
WiFi: For handling Wi-Fi connectivity.
WiFiUdp: For UDP communication.

You can install these libraries by navigating to Sketch > Include Library > Manage Libraries in the Arduino IDE.

3. Writing the Code

You will create two separate programs: one for the server (ESP32 #1) and one for the client (ESP32 #2). The server will manage the game logic, while the client will send paddle movements and receive game state updates.

Program 1: Server (ESP32 #1)

The server listens for UDP packets from the client and updates its game state accordingly.

#include <WiFi.h>
#include <WiFiUdp.h>
#include <U8g2lib.h>

#define BUTTON_UP 2
#define BUTTON_DOWN 4

const char* ssid = "PongGame";  // SSID of Wi-Fi network
const char* password = "12345678";  // Password of Wi-Fi network

WiFiUDP udp;
const unsigned int localUdpPort = 4210;  // Local UDP port for listening
char incomingPacket[255];  // Buffer for incoming packets
IPAddress clientIP;

U8G2_SH1106_128X64_NONAME_F_HW_I2C u8g2(U8G2_R0, U8X8_PIN_NONE);

int paddle1Y = 30, paddle2Y = 30;
int ballX = 64, ballY = 32;
int ballVelX = 1, ballVelY = 1;

void setup() {
  Serial.begin(115200);
  
  pinMode(BUTTON_UP, INPUT_PULLUP);
  pinMode(BUTTON_DOWN, INPUT_PULLUP);

  u8g2.begin();
  u8g2.clearBuffer();

  // Start Wi-Fi as an access point
  WiFi.softAP(ssid, password);
  Serial.println("WiFi AP started");

  udp.begin(localUdpPort);
  Serial.printf("Now listening on UDP port %d\n", localUdpPort);
}

void loop() {
  handleButtons();
  updateGame();
  drawGame();
  sendGameState();
  receivePaddlePosition();
  delay(20);  // Adjust delay for game speed
}

void handleButtons() {
  if (digitalRead(BUTTON_UP) == LOW) {
    paddle1Y -= 2;
    if (paddle1Y < 0) paddle1Y = 0;
  }
  if (digitalRead(BUTTON_DOWN) == LOW) {
    paddle1Y += 2;
    if (paddle1Y > 48) paddle1Y = 48;  // Limit paddle position
  }
}

void updateGame() {
  ballX += ballVelX;
  ballY += ballVelY;

  // Ball collision with top/bottom
  if (ballY <= 0 || ballY >= 64) ballVelY = -ballVelY;

  // Ball collision with paddles
  if (ballX <= 4 && ballY >= paddle1Y && ballY <= paddle1Y + 16) ballVelX = -ballVelX;
  if (ballX >= 124 && ballY >= paddle2Y && ballY <= paddle2Y + 16) ballVelX = -ballVelX;

  // Ball out of bounds
  if (ballX <= 0 || ballX >= 128) {
    ballX = 64;
    ballY = 32;
  }
}

void drawGame() {
  u8g2.clearBuffer();
  u8g2.drawBox(2, paddle1Y, 2, 16);  // Draw paddle 1
  u8g2.drawBox(124, paddle2Y, 2, 16);  // Draw paddle 2
  u8g2.drawDisc(ballX, ballY, 2);  // Draw ball
  u8g2.sendBuffer();
}

void sendGameState() {
  String gameState = String(paddle1Y) + "," + String(ballX) + "," + String(ballY);
  
  // Convert the string to a byte array
  const char* gameStateCStr = gameState.c_str();
  udp.beginPacket(clientIP, localUdpPort);
  udp.write((const uint8_t*)gameStateCStr, strlen(gameStateCStr));  // Send game state to client
  udp.endPacket();
}

void receivePaddlePosition() {
  int packetSize = udp.parsePacket();
  if (packetSize) {
    int len = udp.read(incomingPacket, 255);
    if (len > 0) {
      incomingPacket[len] = 0;
      paddle2Y = atoi(incomingPacket);  // Get paddle 2 position from client
      clientIP = udp.remoteIP();  // Get client IP address
    }
  }
}

Program 2: Client (ESP32 #2)

The client sends its paddle position to the server and receives the game state to update its display.

#include <WiFi.h>
#include <WiFiUdp.h>
#include <U8g2lib.h>

#define BUTTON_UP 2
#define BUTTON_DOWN 4

const char* ssid = "PongGame";  // SSID of Wi-Fi network
const char* password = "12345678";  // Password of Wi-Fi network

WiFiUDP udp;
const char* serverIP = "192.168.4.1";  // IP of the server (Player 1)
const unsigned int localUdpPort = 4210;  // Local UDP port for listening
char incomingPacket[255];  // Buffer for incoming packets

U8G2_SH1106_128X64_NONAME_F_HW_I2C u8g2(U8G2_R0, U8X8_PIN_NONE);

int paddle2Y = 30;
int ballX, ballY, paddle1Y;

void setup() {
  Serial.begin(115200);
  
  pinMode(BUTTON_UP, INPUT_PULLUP);
  pinMode(BUTTON_DOWN, INPUT_PULLUP);

  u8g2.begin();
  u8g2.clearBuffer();

  // Connect to Wi-Fi network
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(1000);
    Serial.println("Connecting to WiFi...");
  }
  Serial.println("Connected to WiFi");

  udp.begin(localUdpPort);
}

void loop() {
  handleButtons();
  sendPaddlePosition();
  receiveGameState();
  drawGame();
  delay(20);  // Adjust delay for game speed
}

void handleButtons() {
  if (digitalRead(BUTTON_UP) == LOW) {
    paddle2Y -= 2;
    if (paddle2Y < 0) paddle2Y = 0;
  }
  if (digitalRead(BUTTON_DOWN) == LOW) {
    paddle2Y += 2;
    if (paddle2Y > 48) paddle2Y = 48;  // Limit paddle position
  }
}

void sendPaddlePosition() {
  String paddlePos = String(paddle2Y);
  const char* paddlePosCStr = paddlePos.c_str();
  udp.beginPacket(serverIP, localUdpPort);
  udp.write((const uint8_t*)paddlePosCStr, strlen(paddlePosCStr));  // Send paddle position to server
  udp.endPacket();
}

void receiveGameState() {
  int packetSize = udp.parsePacket();
  if (packetSize) {
    int len = udp.read(incomingPacket, 255);
    if (len > 0) {
      incomingPacket[len] = 0;
      sscanf(incomingPacket, "%d,%d,%d", &paddle1Y, &ballX, &ballY);  // Update game state
    }
  }
}

void drawGame() {
  u8g2.clearBuffer();
  u8g2.drawBox(2, paddle1Y, 2, 16);  // Draw paddle 1
  u8g2.drawBox(124, paddle2Y, 2, 16);  // Draw paddle 2
  u8g2.drawDisc(ballX, ballY, 2);  // Draw ball
  u8g2.sendBuffer();
}

4. Testing and Troubleshooting

Upload the Code: Upload the server code to one ESP32 and the client code to the other.
Connect to Wi-Fi: Power on the ESP32 boards. The server will create a Wi-Fi access point, and the client will connect to it.
Check Serial Monitor: Open the serial monitor on both boards to ensure they connect correctly.
Adjust Timing: If the game is too fast or too slow, adjust the delay(20) in both codes to fine-tune the game speed.

5. Conclusion

You’ve now built a basic multiplayer Pong game using two ESP32 boards. This project is a great way to explore the capabilities of the ESP32 for real-time applications and communication over Wi-Fi. You can expand on this project by adding features like scoring, sound effects, or even a more sophisticated graphical interface.

Enjoy your game!