# Example server application in Python

This tutorial shows how to set up a simple HTTP server with a database and configure an Efento Gateway to send measurement data to it. In the example, we use **Python**, **Flask**, and a **PostgreSQL** database, but the same concept can easily be implemented in other programming languages or with different databases.

{% hint style="info" %}
If you have any questions or run into issues, feel free to contact us at **help.efento.io**.
{% endhint %}

## Before you start

Before beginning, ensure that you have installed and configured the following components:

* **PyCharm** or any Python 3 IDE
* **PostgreSQL** database
* **Efento Gateway** and **Efento Bluetooth Low Energy loggers**

## PostgreSQL Database Setup

{% stepper %}
{% step %}

### Create the database

After installing PostgreSQL, you will be prompted to create your first database during setup. By default, it will be created using the following credentials:

```
DATABASE_HOST = 'localhost'
DATABASE_USER = 'postgres'
DATABASE_PASSWORD = 'your_password'
DATABASE_NAME = 'postgres'
```

You may change these values if needed. Be sure to write down your credentials, as they will be required later.

To check or modify database credentials, open **pgAdmin**, then navigate to:\
**Object → Properties → General**

<figure><img src="/files/qwUHY9NVBqODHWMmubyd" alt=""><figcaption></figcaption></figure>
{% endstep %}

{% step %}

### Create the measurements table

To store measurements sent from the Efento Gateway, you must create a table. In this example, we create a very simple structure containing five columns, all of type `text`. This design is only for demonstration purposes - your production database should be structured according to your project needs.

You may create the table using pgAdmin’s interface or by running a SQL query.

In pgAdmin, select your database and navigate to:\
**Tools → Query Tool**

<figure><img src="/files/RwOHz5Ff6sERE1SiSkIp" alt=""><figcaption></figcaption></figure>

Insert the query below and click **Execute (▶)**:

```sql
CREATE TABLE measurements (
    measured_at text,
    serial_number text,
    low_battery text,
    type text,
    value text
);
```

Running `CREATE TABLE` creates a new, initially empty table owned by the user who executed the command.
{% endstep %}
{% endstepper %}

## Python Server

The script you will create sets up a simple HTTP server. Efento Gateway sends data as **JSON over REST**, and a single message may contain multiple measurements.

When the server receives a request:

1. It parses the JSON payload.
2. It saves all measurements to the PostgreSQL database.
3. It returns **HTTP 201** to confirm that the data was successfully processed.
4. If something goes wrong (e.g., database connection failure), the server returns **HTTP 503**, and the gateway will automatically retry sending the data later.

<figure><img src="/files/uPqHiHt348AqEFDmLWxj" alt=""><figcaption></figcaption></figure>

{% stepper %}
{% step %}

### Install the required Python components

To run the server, you will need:

* **Flask** – a micro-framework for building web applications\
  Install it via PyCharm or using:

  ```
  pip install -U Flask
  ```
* **psycopg2** – a popular PostgreSQL adapter for Python\
  Install using:

  ```
  pip install psycopg2
  ```

{% endstep %}

{% step %}

### Run the script

Copy the code below into a `.py` file. Update the database credentials, run the script, and the server will begin listening for data from the Efento Gateway.

{% code expandable="true" %}

```python
import psycopg2
from flask import Flask, request, Response, json, g

app = Flask(__name__)

# Enter your database host, database user, database password and database name
DATABASE_HOST = 'DATABASE_HOST'
DATABASE_USER = 'DATABASE_USER'
DATABASE_PASSWORD = 'DATABASE_PASSWORD'
DATABASE_NAME = 'DATABASE_NAME'

# Making the initial connection:
conn = psycopg2.connect(
    dbname=DATABASE_NAME,
    user=DATABASE_USER,
    host=DATABASE_HOST,
    password=DATABASE_PASSWORD
)

# Set up "/api/v4/measurements" endpoint, which will be receiving the data sent by Efento Gateway using POST method.
@app.route('/api/v4/measurements', methods=['POST'])
def respond():
    data = request.json
    record = []
    response_handle = []

    # iteration in list data/measurement
    for measurement in data['measurements']:
        # iteration in list data/measurement/params, creating a list of sensor parameters(measured_at,serial,battery) and measurement results
        for param in measurement['params']:
            record.extend([(measurement['measured_at'], measurement['serial'], measurement['battery'], param['type'],
                            param['value'])])
        response_handle.append(measurement['response_handle'])
    response = json.dumps(({'Y': response_handle, 'N': []}))

    measurements = "INSERT INTO measurements(measured_at, serial_number, low_battery, type, value) VALUES (%s, %s, %s, %s, %s)"
    with conn.cursor() as cur:
        try:
            # inserting a list of sensor parameters and measurement to table in PostgresSQL
            cur.executemany(measurements, record)
            conn.commit()
            cur.close()
        except (Exception, psycopg2.DatabaseError) as error:
            print(error)
            return Response(status="503")
    return Response(response, status="201")

# Start the application on Your port. Default port 5000
if __name__ == "__main__":
    app.run(host='0.0.0.0', port=5000)
```

{% endcode %}
{% endstep %}

{% step %}

### Configure Efento Gateway

#### Ethernet Gateway

1. Log in to the Efento Gateway web panel. Navigate to:\
   **Settings → Server settings**
2. In **Connection to Server**, select **Custom Settings**.
3. Enter the **server address** (your PC/server IP or domain) in the *Server Address* field.
4. Set the **Server Port** to `5000`.
5. Switch **TLS OFF** for this tutorial.

<figure><img src="/files/XzbqUTv5V28FrCIjnAJO" alt=""><figcaption></figcaption></figure>

{% hint style="warning" %}
When TLS is disabled, data is sent unencrypted. For production deployments, always [upload your server certificate in the CA Certificate](/efento-gateways/ethernet-gateway/other-settings.md#custom-ca-certificates) tab and enable encrypted HTTPS communication (TLS - ON).

For development or demonstration purposes you may [use a self-signed certificate](/efento-gateways/integration/self-signing-ca-certificate.md).
{% endhint %}
{% endstep %}
{% endstepper %}

## Results

Once the Python script is running, all data sent from the Efento Gateway will be saved in your PostgreSQL database.

To view measurements:

1. Open **pgAdmin 4**
2. Select your database
3. Go to **Tools → Query Tool**
4. Enter and execute:

```sql
SELECT * FROM measurements;
```

You will now see all measurements received from the Efento Gateway stored in your database.

<figure><img src="/files/8AhQOZmlpshjr4I8yRjw" alt=""><figcaption></figcaption></figure>


---

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