Create a Simple Chat Application Using Socket.IO in C++

A guide on how to create a simple chat application using C++ with Socket.IO, helping you to understand more about network programming and real-time communication.

This article will guide you through building a basic chat application using C++ combined with Socket.IO. We will create a server using Socket.IO and a client that can send and receive messages in real time.

C++ Code

#include <iostream>
#include <uWS/uWS.h>
#include <string>
#include <json.hpp>

using json = nlohmann::json;

int main() {
    uWS::Hub h;

    // When a client connects
    h.onConnection([](uWS::WebSocket<uWS::SERVER>* ws, uWS::HttpRequest req) {
        std::cout << "Client connected!" << std::endl;
    });

    // When a message is received from a client
    h.onMessage([](uWS::WebSocket<uWS::SERVER>* ws, char* message, size_t length, uWS::OpCode opCode) {
        // Convert message to string
        std::string msg = std::string(message, length);
        std::cout << "Received message: " << msg << std::endl;

        // Echo message back to all clients
        ws->send(msg.c_str(), msg.length(), opCode);
    });

    // When a client disconnects
    h.onDisconnection([](uWS::WebSocket<uWS::SERVER>* ws, int code, char* message, size_t length) {
        std::cout << "Client disconnected!" << std::endl;
    });

    // Start the server on port 3000
    if (h.listen(3000)) {
        std::cout << "Server started on port 3000" << std::endl;
    }
    h.run();
    return 0;
}

Detailed explanation:

1. #include <uWS/uWS.h>: Including the uWebSockets library to create a WebSocket server.
2. using json = nlohmann::json;: Using a JSON library to handle JSON data (if needed).
3. h.onConnection(...): Event handler for when a client connects, notifying the connection.
4. h.onMessage(...): Event handler for incoming messages from clients, printing the message and sending it back to all clients.
5. h.onDisconnection(...): Event handler for when a client disconnects, notifying the disconnection.
6. h.listen(3000): Starting the server on port 3000 and checking for success.
7. h.run(): Starting the event processing loop.

System Requirements:

• C++17 or newer
• uWebSockets and nlohmann/json libraries

How to install the libraries needed to run the C++ code above:

1. Install uWebSockets: Follow the guide at uWebSockets GitHub.
2. Install the JSON library: You can use CMake or simply add the json.hpp file to your project.

Tips:

• Experiment with extending features such as chat history or adding notifications for online/offline users.
• Ensure to use encryption for sensitive messages.

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