WebSockets in C++: Building a Real-Time Application from Scratch

Introduction: Why C++ Still Rules in Real-Time?

When it comes to real-time applications — chats, order books, multiplayer games, or monitoring systems — many immediately think of Node.js or Python with asyncio. And that's a mistake. C++ remains the king of performance and low latency. If you need to handle thousands of connections with minimal latency, WebSockets in C++ is the professional's choice.

In this article, we'll break down how to set up a real-time server in C++ using powerful libraries. You'll learn the advantages of C++ over scripting languages and get ready-to-use code examples that you can immediately apply in your projects.

We won't beat around the bush: we'll open a WebSocket connection, send a message, and close the session. Along the way, we'll also look at how it all works under the hood. Let's go!

What is WebSocket and Why Do You Need It in C++?

WebSocket is a protocol that allows establishing a persistent bidirectional connection between a client and a server. Unlike HTTP, where each request is a separate transaction, WebSocket keeps the "pipe" open. This is ideal for real-time C++ applications where every millisecond counts.

Main use cases:

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• Financial terminals: real-time quote updates.
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• Game servers: synchronizing player states.
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• Monitoring systems: transmitting logs and metrics from sensors.
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• Collaborative editors: real-time document editing.
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C++ provides an undeniable advantage here: direct memory control, no GC (garbage collector), and the ability to use asynchronous patterns without virtual machine overhead. If you need to handle 50,000+ concurrent connections, a WebSocket server in C++ will be more stable and faster than the alternatives.

Choosing a Library: Boost.Beast or uWebSockets?

In the C++ ecosystem, there are two main players for working with WebSocket. Let's break down their pros and cons.

Boost.Beast — Industry Standard

Boost.Beast is a library based on Boost.Asio. It gives you full control over the network stack. It is used in production by giants like Facebook (in some internal tools) and financial companies.

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• Pros: maximum flexibility, HTTP+WebSocket support, Asio integration.
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• Cons: high learning curve, lots of code for simple tasks.
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uWebSockets — Lightweight and Fast

uWebSockets (uWS) is a wrapper over the C library uSockets. It is designed for maximum performance and minimal memory consumption. Ideal for microservices.

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• Pros: very fast, simple API, low RAM usage.
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• Cons: smaller community, harder to customize.
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For our example, we'll use Boost.Beast as it offers more learning opportunities. But if you need a simple real-time C++ application under load — take a look at uWS.

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

Let's create a minimal echo server. It will accept connections, read messages, and send them back. This is the classic "Hello World" for WebSocket.

Make sure you have Boost installed (preferably version 1.75+) and a compiler with C++17 support.

#include <boost/beast/core.hpp>\n#include <boost/beast/websocket.hpp>\n#include <boost/asio/ip/tcp.hpp>\n#include <cstdlib>\n#include <functional>\n#include <iostream>\n#include <string>\n#include <thread>\n\nnamespace beast = boost::beast;\nnamespace websocket = beast::websocket;\nnamespace net = boost::asio;\nusing tcp = net::ip::tcp;\n\n// Handling a single Web