WebSocket in C++: Building Real-Time Applications from Scratch

Introduction: Why WebSocket and C++ Are the Perfect Pair for Real-Time

In the modern world of web applications, users are accustomed to instant updates: social media notifications, live chats, stock quotes, online games. The traditional approach with HTTP requests (Polling) creates excessive server load and increases latency. The solution is the WebSocket protocol, which establishes a persistent bidirectional connection between the client and server.

The C++ language is ideal for creating high-load real-time systems due to its performance, low-level memory control, and minimal overhead. In this article, we will explore how to implement a WebSocket server and client in C++ using modern libraries, and discuss best development practices.

WebSocket Basics and Tool Selection

How Does WebSocket Work?

WebSocket is a protocol over TCP that starts with an HTTP handshake and then switches to a binary data transfer mode. After the connection is established, message exchange occurs without additional headers, significantly speeding up transmission.

Key characteristics:

• Full-duplex communication (server and client can send data simultaneously)
• Low latency
• Support for text and binary frames
• Automatic connection management (ping/pong for keep-alive)

Popular Libraries for WebSocket in C++

Several mature solutions exist for working with WebSocket in C++:

• Boost.Beast — part of the Boost library, based on ASIO. Provides full control, ideal for industrial projects.
• uWebSockets (µWebSockets) — a lightweight, high-performance library, often used in conjunction with Node.js or as a standalone server.
• libwebsockets — a cross-platform library with rich functionality (SSL, IPv6).
• IXWebSocket — easy to use, suitable for small projects and prototyping.

In this article, we will focus on Boost.Beast as the most flexible and powerful solution.

Practical Implementation of a WebSocket Server in C++ with Boost.Beast

Project Setup

First, ensure you have a compiler with C++17 support and the Boost library (version 1.75+) installed. Installation via package manager:

# Ubuntu/Debiansudo apt install libboost-all-dev# macOS (Homebrew)brew install boost

Creating a Simple WebSocket Echo Server

Let's look at a basic server example that accepts connections and sends received messages back (echo).

#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 {        // Create a WebSocket stream from the socket        websocket::stream<tcp::socket> ws{std::move(socket)};                // Perform the handshake        ws.accept();

        // Message processing loop        while (true) {            beast::flat_buffer buffer;                        // Read a message from the client            ws.read(buffer);                        // Send the message back (echo)            ws.text(ws.got_text()); // Preserve the message type            ws.write(buffer.data());                        // Print the received message to the console            std::cout << "Received: " << beast::make_printable(buffer.data()) << std::endl;        }    } catch (beast::system_error