#include <WiFi.h>

#define TRIG_PIN 5
#define ECHO_PIN 18
#define RELAY_PIN 26

const char* ssid = "YOUR_WIFI_NAME";
const char* password = "YOUR_WIFI_PASSWORD";

WiFiServer server(23);

long duration;
float distance;
float tankHeight = 30.0;
float waterLevel;
float percentage;

bool autoMode = true;
bool motorState = false;

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

pinMode(TRIG_PIN, OUTPUT);
pinMode(ECHO_PIN, INPUT);
pinMode(RELAY_PIN, OUTPUT);

digitalWrite(RELAY_PIN, HIGH);

Serial.println("Connecting to WiFi...");
WiFi.begin(ssid, password);

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

Serial.println("\nWiFi Connected!");
Serial.print("ESP32 IP Address: ");
Serial.println(WiFi.localIP());

server.begin();
Serial.println("TCP Server Started on Port 23");
}

void loop() {

WiFiClient client = server.available();

if (client) {
Serial.println("Client Connected");

client.println("=== Smart Water Management ===");
client.println("Commands: AUTO, MANUAL, ON, OFF");

while (client.connected()) {

// Ultrasonic Measurement
digitalWrite(TRIG_PIN, LOW);
delayMicroseconds(2);
digitalWrite(TRIG_PIN, HIGH);
delayMicroseconds(10);
digitalWrite(TRIG_PIN, LOW);

duration = pulseIn(ECHO_PIN, HIGH);
distance = duration * 0.034 / 2;

waterLevel = tankHeight - distance;

if (waterLevel < 0) waterLevel = 0;
if (waterLevel > tankHeight) waterLevel = tankHeight;

percentage = (waterLevel / tankHeight) * 100;

client.print("Tank Level: ");
client.print(percentage);
client.println(" %");

if (client.available()) {

String command = client.readStringUntil('\n');
command.trim();

if (command.equalsIgnoreCase("AUTO")) {
autoMode = true;
client.println("Switched to AUTO Mode");
}
else if (command.equalsIgnoreCase("MANUAL")) {
autoMode = false;
client.println("Switched to MANUAL Mode");
}
else if (command.equalsIgnoreCase("ON") && !autoMode) {
turnMotorOn(client);
}
else if (command.equalsIgnoreCase("OFF") && !autoMode) {
turnMotorOff(client);
}
}

// AUTO MODE LOGIC
if (autoMode) {

if (percentage < 20 && !motorState) {
client.println("Water LOW -> Motor ON");
turnMotorOn(client);
}

if (percentage > 90 && motorState) {
client.println("Tank FULL -> Motor OFF");
turnMotorOff(client);
client.println("WARNING: Tank Full!");
}
}

delay(2000);
}

client.stop();
Serial.println("Client Disconnected");
}
}

void turnMotorOn(WiFiClient client) {
digitalWrite(RELAY_PIN, LOW);
motorState = true;
client.println("Motor is ON");
}

void turnMotorOff(WiFiClient client) {
digitalWrite(RELAY_PIN, HIGH);
motorState = false;
client.println("Motor is OFF");
}

🧠 Code Explanation

1️⃣ Connect to Home WiFi

ESP32 connects to your router.

Prints IP address.

Example:

You must use this IP in mobile app.

2️⃣ TCP Server Creation

Creates Telnet server on Port 23.

Mobile connects using:

• Host: ESP32 IP

• Port: 23

3️⃣ Ultrasonic Distance Calculation

Calculates distance in cm.

4️⃣ Tank Percentage Calculation

Gives tank water percentage.

5️⃣ AUTO Mode Logic

If tank < 20%
→ Motor ON

If tank > 90%
→ Motor OFF + Warning

6️⃣ MANUAL Mode Commands

📱 How To Use

Step 1
Upload code

Step 2
Open Serial Monitor
Note ESP32 IP address

Step 3
Connect mobile to same WiFi

Step 4
Open TCP Terminal App

Enter:

• Host: ESP32 IP

• Port: 23

Step 5
Send commands:

📟 Example Output

🎯 What Students Learn

• Home WiFi networking

• TCP client-server communication

• Ultrasonic tank measurement

• Router-based IoT system

• Auto + Manual control logic

• Embedded networking architecture