uwebsockets

uWebSockets Rules

MANDATORY: onData + onAborted

Never use res->onData() without res->onAborted() — the server can crash on client disconnect.

// ✅ CORRECT
res->onData([this, res, buffer = std::move(buffer)](std::string_view data, bool last) mutable {
    buffer.append(data.data(), data.length());
    if (last) { /* process */ }
});
res->onAborted([]() { LOG_WARNING("Request aborted by client"); });

• Always add res->onAborted() after res->onData()
• Use std::move(buffer) in lambda capture
• Check if (last) before processing
• Never access res or controller members after client disconnect

Full POST Template

void Controller::safePostEndpoint(uWS::HttpResponse<false>* res, uWS::HttpRequest* req) {
    std::string buffer;
    res->onData([this, res, buffer = std::move(buffer)](std::string_view data, bool last) mutable {
        buffer.append(data.data(), data.length());
        if (last) {
            try {
                auto jsonBody = nlohmann::json::parse(buffer);
                // ... business logic ...
                this->json(res, response);
            } catch (const std::exception& e) {
                LOG_ERROR("Error in endpoint: " + std::string(e.what()));
                serverError(res, "Processing error");
            }
        }
    });
    res->onAborted([]() { LOG_WARNING("Client disconnected during request processing"); });
}

Common crash: "Empty reply from server" or segfault in POST → add onAborted().