✅ ESP32 + DHT11 + WiFi Terminal (Hotspot Mode)

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

// ——————– Hotspot (Access Point) Details ——————–
const char* ap_ssid = “ESP32_DHT11”;
const char* ap_password = “12345678”; // Minimum 8 characters

// ——————– DHT Setup ——————–
#define DHTPIN 4
#define DHTTYPE DHT11

DHT dht(DHTPIN, DHTTYPE);

// ——————– WiFi Server Setup ——————–
// Port 23 = Telnet (WiFi Terminal Apps mostly use this)
WiFiServer server(23);
WiFiClient client;

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

// Start DHT sensor
dht.begin();

// ——————– Start ESP32 Hotspot ——————–
WiFi.softAP(ap_ssid, ap_password);

// Get ESP32 Hotspot IP Address (Usually 192.168.4.1)
IPAddress IP = WiFi.softAPIP();

Serial.println(“✅ ESP32 Hotspot Started!”);
Serial.print(“📶 Hotspot Name (SSID): “);
Serial.println(ap_ssid);

Serial.print(“🔑 Password: “);
Serial.println(ap_password);

Serial.print(“🌐 Hotspot IP Address: “);
Serial.println(IP);

// ——————– Start WiFi Terminal 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 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(” %”);

// ——————– Also 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.

✅ Step 2: Open Serial Monitor (115200)

You will see something like:

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✅ Step 3: Connect Phone to ESP32 Hotspot

Open WiFi settings in phone and connect to:

📶 WiFi Name: ESP32_DHT11
🔑 Password: 12345678

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✅ Step 4: Open WiFi Terminal App

In the terminal app, set:

• Host / IP: 192.168.4.1

• Port: 23

Then press Connect

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✅ Output on Phone Terminal

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🧠 FULL DETAILED CODE EXPLANATION (Teaching Style)

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✅ 1) Include Libraries

🔹 WiFi.h

Used to:

• Create hotspot

• Create WiFi server

• Accept client connection

🔹 DHT.h

Used to:

• Read temperature

• Read humidity

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✅ 2) Hotspot Name & Password

This sets the WiFi hotspot details.

📌 Rules:

• Password must be minimum 8 characters

• SSID can be any name

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✅ 3) DHT Sensor Setup

• DHT data pin connected to GPIO4

• Sensor type is DHT11

• Creates DHT object

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✅ 4) Create WiFi Server

🔹 WiFiServer server(23)

This creates a TCP server on port 23.

Port 23 is standard for Telnet.

Most WiFi terminal apps use this.

🔹 WiFiClient client

This stores the phone connection.

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✅ 5) setup() Function

Runs once.

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🔹 Start Serial Monitor

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🔹 Start DHT sensor

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🔹 Start Hotspot

This makes ESP32 act like a WiFi router.

Now your phone can connect to ESP32.

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🔹 Get Hotspot IP

ESP32 hotspot IP is usually:

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🔹 Start server

This starts the WiFi terminal server.

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✅ 6) loop() Function

Runs forever.

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🔹 Check if phone connected

This means:

• If no phone is connected → wait

• When phone connects → store that connection

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🔹 Delay for DHT11

DHT11 needs 2 seconds gap.

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🔹 Read sensor

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🔹 Check error

If wiring wrong or sensor fails, values become NAN.

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🔹 Send output to phone terminal

This prints on WiFi terminal app.

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🔹 Print on Serial Monitor also

So you can debug on laptop also.

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⚠ Common Problems & Fix

❌ Phone not connecting

✅ Connect phone WiFi first: ESP32_DHT11

❌ Terminal not connecting

Use:

• IP: 192.168.4.1

• Port: 23

❌ Port blocked

Change port 23 to 8080:

Then in terminal app:

• Port = 8080