drogon/examples/websocket_server/WebSocketServer.cc

#include <drogon/WebSocketController.h>
#include <drogon/PubSubService.h>
#include <drogon/HttpAppFramework.h>
using namespace drogon;

class WebSocketChat : public drogon::WebSocketController<WebSocketChat>
{
  public:
    virtual void handleNewMessage(const WebSocketConnectionPtr &,
                                  std::string &&,
                                  const WebSocketMessageType &) override;
    virtual void handleConnectionClosed(
        const WebSocketConnectionPtr &) override;
    virtual void handleNewConnection(const HttpRequestPtr &,
                                     const WebSocketConnectionPtr &) override;
    WS_PATH_LIST_BEGIN
    WS_PATH_ADD("/chat", Get);
    WS_PATH_LIST_END
  private:
    PubSubService<std::string> chatRooms_;
};

struct Subscriber
{
    std::string chatRoomName_;
    drogon::SubscriberID id_;
};
void WebSocketChat::handleNewMessage(const WebSocketConnectionPtr &wsConnPtr,
                                     std::string &&message,
                                     const WebSocketMessageType &type)
{
    // write your application logic here
    LOG_DEBUG << "new websocket message:" << message;
    if (type == WebSocketMessageType::Ping)
    {
        LOG_DEBUG << "recv a ping";
    }
    else if (type == WebSocketMessageType::Text)
    {
        auto &s = wsConnPtr->getContextRef<Subscriber>();
        chatRooms_.publish(s.chatRoomName_, message);
    }
}

void WebSocketChat::handleConnectionClosed(const WebSocketConnectionPtr &conn)
{
    LOG_DEBUG << "websocket closed!";
    auto &s = conn->getContextRef<Subscriber>();
    chatRooms_.unsubscribe(s.chatRoomName_, s.id_);
}

void WebSocketChat::handleNewConnection(const HttpRequestPtr &req,
                                        const WebSocketConnectionPtr &conn)
{
    LOG_DEBUG << "new websocket connection!";
    conn->send("haha!!!");
    Subscriber s;
    s.chatRoomName_ = req->getParameter("room_name");
    s.id_ = chatRooms_.subscribe(s.chatRoomName_,
                                 [conn](const std::string &topic,
                                        const std::string &message) {
                                     // Supress unused variable warning
                                     (void)topic;
                                     conn->send(message);
                                 });
    conn->setContext(std::make_shared<Subscriber>(std::move(s)));
}

int main()
{
    app().addListener("127.0.0.1", 8848).run();
}