WebSocket in C++: Real-Time Applications from A to Z

WebSocket in C++: Real-Time Applications from A to Z

In the modern world of web technologies, users expect instant responses from applications. The traditional HTTP protocol, operating on a "request-response" model, is poorly suited for tasks requiring constant data updates: online chats, stock quotes, multiplayer games, and monitoring systems. This is where WebSocket comes to the rescue — a protocol that provides a persistent bidirectional connection between client and server.

In this article, we will explore how to create real-time applications in C++ using WebSocket. You will learn about libraries, architecture, and write your first working code.

What is WebSocket and why is it needed in C++?

WebSocket is a protocol that establishes a persistent TCP connection between client and server. After the handshake, data can be transmitted in both directions without the need for repeated HTTP requests. This dramatically reduces latency and network load.

C++ is an ideal language for high-performance real-time systems. It gives you full control over memory, threads, and network operations. Combined with WebSocket, you get:

• Minimal latency — data is delivered in milliseconds.
• High throughput — thousands of simultaneous connections.
• Energy efficiency — low server resource consumption.

Use cases: trading terminals, online games (e.g., real-time chess), notification systems, IoT devices, and even sensor data streaming.

Library Selection: Boost.Beast vs uWebSockets

There are several popular C++ libraries for working with WebSocket. We will consider two main ones:

Boost.Beast

This is part of the Boost ecosystem, written in modern C++11/14/17. Beast provides low-level control over WebSocket and HTTP. It is asynchronous, based on Boost.Asio, and is ideal for serious projects.

uWebSockets (µWebSockets)

A lightweight and ultra-fast library. Written in C++17, focused on maximum performance. Ideal for microservices and simple real-time applications.

For this guide, we will choose Boost.Beast, as it is more flexible and better documented for educational purposes.

Writing a WebSocket Server in C++ with Boost.Beast

Let's create a simple echo server that receives messages from the client and sends them back. This is the foundation for any real-time application.

First, install Boost.Beast and Asio. On most Linux distributions, this is done via the package manager:

sudo apt install libboost-all-dev

Now the server code:

#include <boost/beast/core.hpp>#include <boost/beast/websocket.hpp>#include <boost/asio/ip/tcp.hpp>#include <iostream>#include <string>#include <thread>

namespace beast = boost::beast;namespace websocket = beast::websocket;namespace net = boost::asio;using tcp = net::ip::tcp;

void do_session(tcp::socket&& socket) {    try {        websocket::stream<tcp::socket> ws{std::move(socket)};        ws.accept();

        for (;;) {            beast::flat_buffer buffer;            ws.read(buffer);            auto msg = beast::buffers_to_string(buffer.data());            std::cout << "Received: " << msg << std::endl;

            // Echo response            ws.text(ws.got_text());            ws.write(buffer.data());        }    } catch (beast::system_error const& se) {        if (se.code() != websocket::error::closed) {            std::cerr << "Error: " << se.code().message() << std::endl;        }    }}

int main() {    try {