How is data exchange and interaction between the client and server parts of the application implemented?

Data exchange between the client and server parts of an application usually occurs through network protocols, most commonly HTTP/HTTPS. The client (for example, a web browser or a mobile app) sends requests to the server, which processes them and returns responses.

Main interaction methods:

• REST API — the client sends HTTP requests (GET, POST, PUT, DELETE) to the server, which returns data in JSON or XML format.
• WebSocket — for two-way real-time data exchange.
• GraphQL — allows the client to request only the needed data.

Example in Python using Flask to create a simple REST API:

from flask import Flask, jsonify, request

app = Flask(__name__)

@app.route('/data', methods=['GET'])
def get_data():
    data = {'message': 'Hello from the server!'}
    return jsonify(data)

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

The client can send a GET request to /data and receive a JSON message. Thus, the client and server interact through requests and responses, exchanging data in standardized formats.