✅ ESP32 + DHT11 + WiFi Terminal (Connect to Running WiFi)

#include <WiFi.h>
#include <DHT.h>

// -------------------- WiFi Credentials --------------------
const char* ssid = "YOUR_WIFI_NAME";
const char* password = "YOUR_WIFI_PASSWORD";

// -------------------- DHT Setup --------------------
#define DHTPIN 4
#define DHTTYPE DHT11

DHT dht(DHTPIN, DHTTYPE);

// -------------------- WiFi Server Setup --------------------
// Port 23 = Telnet Terminal Port
WiFiServer server(23);
WiFiClient client;

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

// Start DHT Sensor
dht.begin();

// -------------------- Connect ESP32 to WiFi --------------------
Serial.print("Connecting to WiFi: ");
Serial.println(ssid);

WiFi.begin(ssid, password);

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

Serial.println("\n✅ WiFi Connected Successfully!");
Serial.print("🌐 ESP32 IP Address: ");
Serial.println(WiFi.localIP());

// -------------------- Start WiFi Server --------------------
server.begin();
Serial.println("✅ WiFi Terminal Server Started on Port 23");
}

void loop() {
// -------------------- Wait for Client Connection --------------------
if (!client || !client.connected()) {
client = server.available();
return;
}

// DHT11 needs 2 seconds delay between readings
delay(2000);

// -------------------- Read DHT11 Data --------------------
float humidity = dht.readHumidity();
float temperature = dht.readTemperature();

// -------------------- Check for Sensor Error --------------------
if (isnan(humidity) || isnan(temperature)) {
client.println("❌ Failed to read from DHT11 sensor!");
Serial.println("❌ Failed to read from DHT11 sensor!");
return;
}

// -------------------- Send Data to WiFi Terminal --------------------
client.print("🌡 Temperature: ");
client.print(temperature);
client.print(" °C | ");

client.print("💧 Humidity: ");
client.print(humidity);
client.println(" %");

// -------------------- Print on Serial Monitor --------------------
Serial.print("Temperature: ");
Serial.print(temperature);
Serial.print(" °C | Humidity: ");
Serial.print(humidity);
Serial.println(" %");
}

🔌 Wiring (DHT11 → ESP32)

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📱 How to Use WiFi Terminal App (Step-by-Step)

✅ Step 1: Upload Code

Upload to ESP32.

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✅ Step 2: Open Serial Monitor (115200)

You will see output like:

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✅ Step 3: Connect Phone to SAME WiFi

Your phone must be connected to the same WiFi router.

Example:

• ESP32 connected to: WiFi Router

• Phone also connected to: WiFi Router

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✅ Step 4: Open WiFi Terminal App

Enter:

• Host/IP: 192.168.1.25 (your ESP32 IP)

• Port: 23

Press Connect

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✅ Output in Terminal App

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🧠 FULL DETAILED CODE EXPLANATION (Teaching Style)

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✅ 1) Libraries

🔹 WiFi.h

Used for:

• Connecting ESP32 to WiFi

• Creating TCP server

• Sending data to phone app

🔹 DHT.h

Used for:

• Reading temperature

• Reading humidity

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✅ 2) WiFi Credentials

This is your router WiFi name and password.

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✅ 3) DHT Setup

• GPIO4 is used as DHT data pin

• DHT11 sensor type selected

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✅ 4) Create WiFi Terminal Server

🔹 server(23)

Creates a TCP server on port 23.

Terminal apps connect to port 23 using Telnet style.

🔹 client

Stores the phone connection.

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✅ 5) setup() Runs once

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🔹 Start Serial

For debugging and IP display.

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🔹 Start DHT

Initializes sensor.

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🔹 Connect to WiFi

Starts WiFi connection.

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🔹 Wait until connected

This loop runs until ESP32 gets WiFi connection.

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🔹 Print IP Address

This is the IP you will use in terminal app.

Example:

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🔹 Start Server

Starts the TCP server.

Now phone can connect.

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✅ 6) loop() Runs forever

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🔹 Check phone connected

Meaning:

• If phone not connected → wait

• If phone connects → store connection

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🔹 Delay 2 seconds

Required for DHT11.

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🔹 Read sensor values

Reads sensor.

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🔹 Check NAN error

If sensor fails, values become NAN.

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🔹 Send to terminal app

This sends output to phone WiFi terminal.

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⚠ Common Issues & Fix

❌ Terminal not connecting

✅ Check:

• Phone and ESP32 must be on SAME WiFi

• Correct IP address

• Correct port 23

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❌ Port 23 not working

Change to 8080:

Then terminal port = 8080