C# MQTT客户端--M2MQTT

m2mqtt库：https://github.com/eclipse/paho.mqtt.m2mqtt
m2mqtt手册：https://m2mqtt.wordpress.com/using-mqttclient/
m2mqtt下载：https://www.nuget.org/packages/M2Mqtt/

准备

• 本客户端使用VS2015进行开发，所以需要实现安装VS2015。
• 开发之前需要下载M2MQTT库。m2mqtt库的获取，可以使用vs的nuget来获取。
• 如果VS2015没有NuGet包管理器，可以按照https://jingyan.baidu.com/article/066074d636fd19c3c21cb0a2.html安装。
• 重启VS2015后，打开自己的C#工程，然后打开“工具”-“Nuget包管理器”-“程序包管理器控制台”
  在控制台中输入“Install-Package M2Mqtt -Version 4.3.0”即可自动完成配置。

代码

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;using System.Net;using System.Security.Cryptography.X509Certificates;using uPLibrary.Networking.M2Mqtt;using uPLibrary.Networking.M2Mqtt.Messages;using System.Net.Security;namespace m2mqtt_test{    class Program    {        static void messageReceive(object sender, MqttMsgPublishEventArgs e)        {            string msg = "Topic:" + e.Topic + "   Message:" + System.Text.Encoding.Default.GetString(e.Message);            Console.WriteLine(msg);        }        static bool cafileValidCallback(object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors sslPolicyErrors)        {            string msg = "X509 链状态:";            foreach (X509ChainStatus status in chain.ChainStatus)            {                msg += status.StatusInformation + "\n";            }            msg += "SSL策略问题：" + (int)sslPolicyErrors;            Console.WriteLine(msg);            if (sslPolicyErrors != SslPolicyErrors.None)                return false;            return true;        }        static void Main(string[] args)        {            string brokerHostName = "192.168.1.38";            int brokerPort = 8883;            string clientId = "m2mqtt";            string username = "develop";            string password = "666666";            string[] topic = {"topic"};            byte[] qosLevels = { MqttMsgBase.QOS_LEVEL_AT_MOST_ONCE};            string caPath = "C:/MqttSSL/ca.crt";            X509Certificate caCert = new X509Certificate(caPath);            Console.WriteLine(caCert.ToString(true)+"\n"+caCert.ToString());            Console.ReadKey();            Console.WriteLine("------------------------分割线-------------------------------");            //无SSL连接            //MqttClient client = new MqttClient(brokerHostName,brokerPort,false,null,null,MqttSslProtocols.None);            try {                //单向SSL通信                MqttClient client = new MqttClient(brokerHostName, brokerPort, true, caCert, null, MqttSslProtocols.TLSv1_2, new RemoteCertificateValidationCallback(cafileValidCallback));                //消息接受                client.MqttMsgPublishReceived += new MqttClient.MqttMsgPublishEventHandler(messageReceive);                //连接Broker                client.Connect(clientId, username, password);                client.Subscribe(topic, qosLevels);            }            catch (System.Exception)            {                Console.WriteLine("连接失败!");                Console.ReadKey();            }        }    }}

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• 本客户端连接Broker是mosquitto，可以到本人的博客找到:http://blog.csdn.net/sxpsxp12/article/details/77870109
• 可能C#遇到的问题：一个是因为客户端和服务端以及签发机构的证书信息相同，导致客户端和服务端不能识别证书，导致连接失败。另外一个原因是因为自己生成的证书没有添加到系统的根证书中，不被根证书所信任导致连接失败。