Experiment: Wi-Fi Connectivity and TCP/IP-Based Sensor Data Transmission Using ESP32/Raspberry Pi

Aim

To configure and implement an IoT device using ESP32 or Raspberry Pi to connect to a Wi-Fi network and transmit temperature and humidity data from a DHT11 sensor to a remote computer using TCP/IP communication.

Objectives

To understand Wi-Fi connectivity in IoT devices.
To interface a DHT11 temperature and humidity sensor with ESP32 or Raspberry Pi.
To understand TCP/IP communication and socket programming.
To establish a TCP connection between an IoT device and a remote computer.
To transmit and receive sensor data over a Wi-Fi network.

Components Required

Sr. No.	Component	Quantity
1	ESP32 Development Board (COG-E32) or Raspberry Pi 4 (COG-RPI4)	1
2	DHT11 Temperature and Humidity Sensor (COG-MSBA)	1
3	USB data cable or Raspberry Pi power supply	1
4	Patch cords	As required
5	Computer with Arduino IDE or Python	1
6	Remote computer connected to the same Wi-Fi network	1
7	Wi-Fi network	1

Theory

Internet of Things (IoT) Device

An IoT device is a physical device equipped with sensors, processing capabilities, and communication interfaces. It collects data from its surroundings and transmits the information to another device or a remote server.

In this experiment, the ESP32 or Raspberry Pi acts as the IoT device. The DHT11 sensor collects temperature and humidity readings, which are transmitted to a remote computer.

Wi-Fi Connectivity

Wi-Fi is a wireless networking technology based on IEEE 802.11 standards. It allows IoT devices to connect to a local wireless network and exchange information with other devices.

The ESP32 has built-in Wi-Fi connectivity. The Raspberry Pi 4 also supports Wi-Fi connectivity.

TCP/IP Communication

TCP/IP is a protocol suite used for communication between devices over a network.

IP (Internet Protocol): Provides addressing and routing of data packets between devices.
TCP (Transmission Control Protocol): Provides reliable, ordered, connection-oriented data delivery.
Socket: A software interface used by applications to send and receive data over a network.

In this experiment, the remote computer runs a TCP server that listens for incoming connections. The ESP32 or Raspberry Pi acts as a TCP client and sends sensor readings to the server.

DHT11 Sensor

The DHT11 is a digital temperature and humidity sensor. It provides temperature and relative humidity readings through a single digital data interface.

Typical measurement ranges are:

Temperature: 0°C to 50°C.
Relative humidity: 20% to 90%.

The DHT11 is suitable for basic environmental monitoring demonstrations. Its accuracy and measurement range are limited compared with more advanced sensors.

System Architecture

       DHT11 Sensor
            |
            v
     +----------------+
     | ESP32 /        |
     | Raspberry Pi   |
     +----------------+
            |
        Wi-Fi Network
            |
            v
     +----------------+
     | Remote Computer|
     | TCP Server     |
     +----------------+
            |
            v
     Display Sensor Data

Pin Connections

ESP32 Connections

ESP32 Pin	DHT11 Pin	Description
3V3	VCC	Sensor power supply
GPIO 4	DATA	Digital data interface
GND	GND	Common ground

Raspberry Pi Connections

Raspberry Pi Pin	DHT11 Pin	Description
Physical Pin 1 (3.3V)	VCC	Sensor power supply
Physical Pin 7 (GPIO4)	DATA	Digital data interface
Physical Pin 6 (GND)	GND	Common ground

Note: The connections assume a compatible DHT11 module with clearly identified VCC, DATA, and GND pins. Verify the actual sensor-board pinout. Raspberry Pi GPIO operates at 3.3V and is not 5V tolerant. Use only a data interface with suitable 3.3V logic levels.

Software Requirements

ESP32

Arduino IDE
ESP32 board support package
DHT sensor library
Wi-Fi library included with the ESP32 board package

Raspberry Pi

Raspberry Pi OS
Python 3
Adafruit CircuitPython DHT library
Blinka library
TCP socket module (Python standard library)

Remote Computer

Python 3
TCP server program
Network access from the IoT device

Program 1: TCP Server on Remote Computer

The remote computer acts as a TCP server. It listens on port 5000 and displays the sensor data received from the IoT device.

Download the program: TCP Server and IoT Client Programs ZIP

Program 2: ESP32 TCP Client

The ESP32 connects to the Wi-Fi network, reads the DHT11 sensor values, and sends the readings to the remote computer using TCP.

Download the program: ESP32 TCP Client Program

Program 3: Raspberry Pi TCP Client

The Raspberry Pi acts as a TCP client. It reads the DHT11 sensor and transmits the data to the remote computer.

Download the program: Raspberry Pi TCP Client Program

Procedure

Step 1: Configure the Remote Computer

Connect the remote computer to the Wi-Fi network.
Find its local IP address using the appropriate network command.
Replace the example IP address in the IoT client program with the remote computer's actual IP address.
Save the TCP server program as tcp_server.py.
Run the server using Python:

<syntaxhighlight lang="bash"> python tcp_server.py </syntaxhighlight>

Ensure that the firewall allows incoming TCP connections on port 5000.

Step 2: Configure ESP32

Connect the DHT11 sensor to the ESP32 using the specified pin connections.
Open Arduino IDE.
Install the DHT sensor library if it is not already installed.
Enter the Wi-Fi SSID, password, and remote computer IP address in the program.
Select the appropriate ESP32 board and COM port.
Upload the program.
Open the Serial Monitor at 115200 baud.
Observe the Wi-Fi connection status and TCP transmission messages.

Step 3: Configure Raspberry Pi (Alternative)

Connect the DHT11 sensor to the Raspberry Pi.
Ensure that Raspberry Pi OS is connected to the same Wi-Fi network as the remote computer.
Install the required Python libraries in the appropriate Python environment.
Enter the remote computer's IP address in the Python client program.
Run the program:

<syntaxhighlight lang="bash"> python tcp_client.py </syntaxhighlight>

Observe the sensor readings on the Raspberry Pi terminal and the remote computer.

Step 4: Verify TCP/IP Communication

Check that the remote computer reports an incoming TCP connection.
Observe the temperature and humidity data received by the server.
Compare the transmitted values with the sensor readings displayed by the IoT device.
Stop the client program and observe the disconnection message on the server.

Observations

Sr. No.	Temperature (°C)	Relative Humidity (%)	Transmission Status
1	Record measured value	Record measured value	Successful / Failed
2	Record measured value	Record measured value	Successful / Failed
3	Record measured value	Record measured value	Successful / Failed

Expected output on the remote computer:

TCP Server started
Waiting for IoT device connection...
Connected by: ('192.168.1.105', 54321)
Received: Temperature: 28.0 C, Humidity: 65.0 %
Received: Temperature: 28.0 C, Humidity: 64.0 %
Received: Temperature: 29.0 C, Humidity: 64.0 %

The above values and IP addresses are illustrative examples, not actual measurements.

Result

An IoT application was implemented using an ESP32 or Raspberry Pi and a DHT11 sensor. The device connected to a Wi-Fi network and transmitted temperature and humidity readings to a remote computer using TCP/IP socket communication.

Viva Questions

What is the role of Wi-Fi in an IoT application?
What is the difference between TCP and UDP?
What is an IP address?
What is a TCP socket?
What is the difference between a TCP client and a TCP server?
Why is TCP considered a reliable communication protocol?
What is the function of the bind() function in Python socket programming?
What is the purpose of the listen() and accept() functions?
What is the function of sendall() in Python?
Why should the remote computer's IP address be configured in the IoT device?
What is the difference between local and public IP addresses?
How can the application be extended to store sensor readings in a database or cloud platform?