sioxx#

A modern Socket.IO client for C++#

sioxx is a C++ Socket.IO client built on Boost.Asio, Boost.Beast and nlohmann/json. It speaks Engine.IO v4 and gives C++ applications the familiar Socket.IO model: connect a client, open namespace sockets, listen for events, emit values, and handle acknowledgements.

sioxx::client client;
auto chat = client.socket("/chat");

chat->on("message", [](const std::string&, sioxx::message data) {
    std::cout << data.dump() << '\n';
});

client.connect("wss://example.com");

Why sioxx?#

The established C++ Socket.IO client carries its own JSON and WebSocket stacks and predates modern target-based CMake. sioxx was created for applications that already use Boost and nlohmann/json and should not need a second set of overlapping dependencies.

Its public API keeps the small, event-driven shape expected from a Socket.IO client while rebuilding the protocol and transport layers around current C++ libraries. The design and implementation trade-offs are described in sioxx — a modern C++ socket.io client.

Features#

  • Engine.IO v4 and Socket.IO namespace support.

  • WebSocket and secure WebSocket transports through Boost.Beast and OpenSSL.

  • HTTP long-polling fallback, or a polling-only mode when required.

  • JSON and MessagePack wire protocols selectable for each client.

  • Custom parser strategies for other wire formats.

  • Event listeners, event emission, acknowledgements, and lifecycle callbacks.

  • Configurable reconnection with capped exponential back-off and jitter.

  • Modern CMake targets, installation, and downstream find_package(sioxx).

Architecture#

The public API separates Socket.IO packet handling from the Engine.IO connection and its concrete transports. A parser strategy translates between Socket.IO packets and Engine.IO message frames, while namespace sockets route events and acknowledgements back to the application.

Layered architecture of the sioxx library

Where to go next#

Read Examples for complete usage patterns or go directly to the sioxx API Reference reference.