1. Introduction

In this tutorial, we will learn how to handle HTTP requests and responses using a Flask-based API. We will be working primarily with JSON data, which is a common data format used in modern web applications.

By the end of this tutorial, you will be able to:
- Understand how to receive and send HTTP requests and responses using Flask.
- Work with JSON data in your Flask app.
- Handle different kinds of HTTP methods like GET, POST, PUT, DELETE.

Prerequisites:
- Basic understanding of Python programming.
- Familiarity with Flask (a Python web framework).
- Understanding of HTTP protocol would be a plus.

2. Step-by-Step Guide

HTTP (HyperText Transfer Protocol) is the foundation of any data exchange on the web. Flask, being a micro web framework provides all the necessary tools to build robust web applications. It handles HTTP requests through the request object and sends HTTP responses through the response object.

HTTP Methods

The HTTP protocol defines several methods indicating the desired action to be performed on the resource. The most commonly used methods are:
- GET: Retrieve data.
- POST: Send data.
- PUT: Update data.
- DELETE: Remove data.

JSON Data

JSON (JavaScript Object Notation) is a lightweight data-interchange format. It is easy for humans to read and write, and easy for machines to parse and generate.

3. Code Examples

Let's dive into some code examples that demonstrate how to handle HTTP requests and responses with Flask.

Example 1: Simple GET Request

from flask import Flask, jsonify, request

app = Flask(__name__)

@app.route('/api', methods=['GET'])
def get_data():
    data = {'name': 'John', 'age': 30, 'city': 'New York'}
    return jsonify(data), 200

if __name__ == '__main__':
    app.run(debug=True)

In this example, we've set up a basic Flask app that responds to a GET request on the '/api' endpoint. The jsonify function is used to convert the Python dictionary into a JSON response.

Example 2: POST Request

@app.route('/api', methods=['POST'])
def post_data():
    data = request.get_json()  # get the incoming data
    if 'name' not in data:
        return "Error: No name field provided", 400
    return jsonify(data), 201

Here, we're handling a POST request on the same '/api' endpoint. The request.get_json() function is used to parse the incoming JSON data.

4. Summary

In this tutorial, we covered the basics of handling HTTP requests and responses in a Flask app, focusing on GET and POST methods. We also learned how to work with JSON data.

Next, try to explore other HTTP methods like PUT and DELETE, and learn how to handle errors in your Flask app. You can also delve deeper into Flask by understanding its routing mechanism, template engine, and more.

5. Practice Exercises

1. Create a Flask app that responds to a GET request with a list of all users from a dummy data set.
2. Extend the app to allow the addition of a new user through a POST request.
3. Further extend the app to update an existing user's data with a PUT request.

Remember, practice is key to mastering any new concept. Happy coding!