MQTTnet客户端发布

Question

我想我的问题是，我每次调用该函数时都会生成新的MQTT客户端。但我不知道如何解决这个问题。我尝试在调用“发布”任务时连接客户端，但随后应用程序就崩溃了。如果我把一个发布部分放在连接函数后面，消息就会被发布。我只是不知道如何在每次调用函数时不被强制生成var MQTTclient新函数。我可能是在监督一些事情，因为我是C#的新手，从来没有用过这个库。

namespace InfiniLight
{
    public class MQTT
    {       

        public static async Task<bool> Publish(string channel, string value)
        {
            var factory = new MqttFactory();
            var mqttClient = factory.CreateMqttClient();

            if (mqttClient.IsConnected == false)
            {
                Debug.WriteLine("publishing failed");
                return false; 
            } 

            var message = new MqttApplicationMessageBuilder()
                    .WithTopic(channel)
                    .WithPayload(value)
                    .WithExactlyOnceQoS()
                    .WithRetainFlag()
                    .Build();
            await mqttClient.PublishAsync(message);
            return true;
        }


        //connect to mqtt

        public static async Task Connect()
        {
            var factory = new MqttFactory();
            var mqttClient = factory.CreateMqttClient();

            string clientId = Guid.NewGuid().ToString();
            string mqttURI = Preferences.Get("broker_ip", "");
            string mqttUser = Preferences.Get("client_username", "");
            string mqttPassword = Preferences.Get("client_password", "");
            int i;
            i = System.Convert.ToInt32(Preferences.Get("broker_port", "1883"));
            int mqttPort = i;
            bool mqttSecure = false;
            var messageBuilder = new MqttClientOptionsBuilder()
              .WithClientId(clientId)
              .WithCredentials(mqttUser, mqttPassword)
              .WithTcpServer(mqttURI, mqttPort)
              .WithCleanSession();
            var options = mqttSecure
              ? messageBuilder
                .WithTls()
                .Build()
              : messageBuilder
                .Build();

            Debug.WriteLine("MQTT: connecting");
            await mqttClient.ConnectAsync(options, CancellationToken.None);
            Debug.WriteLine("MQTT: connected");

            /*
            var message = new MqttApplicationMessageBuilder()                                       
//here it does send the message
                   .WithTopic("hey")
                   .WithPayload("I'm a mobile")
                   .WithExactlyOnceQoS()
                   .WithRetainFlag()
                   .Build();
            await mqttClient.PublishAsync(message); */


        } 

    }

}

Answer 1

将mqttClient更改为类的静态成员，而不是局部变量。然后在调用Publish()之前创建连接，或者在Publish()中创建一次连接，并使用一个条件检查它是否已经连接。无论哪种方式，您都可以重用相同的对象，而不必重新创建它。