add push notification example.

examples/server/main.cpp

@@ -85,6 +85,57 @@ std::string echo(rpc_conn conn, const std::string& src) {
 	return src;
 }
 
+struct notifier {
+public:
+	notifier() {
+		std::thread thd([this] {
+			while (!stop_) {
+				if (has_subs_) {
+					notify("this a notification from the server");
+				}
+
+				std::this_thread::sleep_for(std::chrono::seconds(1));
+			}
+		});
+		thd.detach();
+	}
+
+	~notifier() {
+		stop_ = true;
+	}
+
+	void sub(rpc_conn conn) {
+		if (!has_subs_) {
+			has_subs_ = true;
+		}
+		auto req_id = conn.lock()->request_id();
+		std::unique_lock<std::mutex> lock(mtx_);
+		subs_.emplace_back(conn, req_id);
+	}
+
+private:
+	void notify(const std::string& result) {
+		{
+			std::unique_lock<std::mutex> lock(mtx_);
+			for (auto& pair : subs_) {
+				auto sp_conn = pair.first.lock();
+				if (sp_conn) {
+					sp_conn->pack_and_response(pair.second, result);
+				}
+			}
+
+			subs_.clear();
+		}
+
+		has_subs_ = false;
+	}
+
+	std::vector<std::pair<rpc_conn, uint64_t>> subs_;
+	std::mutex mtx_;
+	std::atomic_bool has_subs_ = { false };
+	bool stop_ = false;
+};
+
 int main() {
 	rpc_server server(9000, std::thread::hardware_concurrency());
 
@@ -100,6 +151,9 @@ int main() {
 	server.register_handler<ExecMode::async>("async_echo", async_echo);
 	server.register_handler("echo", echo);
 
+	notifier n;
+	server.register_handler<ExecMode::async>("sub", &notifier::sub, &n);
+
 	server.run();
 
 	std::string str;