AWS Lambda から AWS IoT に publish したメッセージを C# で MQTTライブラリを使って受信する https://blog.r3it.com/

Program.cs

using System;
using System.Diagnostics;
using System.Text;
using System.Security.Cryptography.X509Certificates;

using uPLibrary.Networking.M2Mqtt;
using uPLibrary.Networking.M2Mqtt.Messages;


        private const string IotEndpoint = "endpoint.iot.ap-northeast-1.amazonaws.com";
        private MqttClient client;

        private void connectMqtt()
        {
            var caCert = new X509Certificate(Properties.Resources.root);
            var clientCert = new X509Certificate2(Properties.Resources.pfx, @"");

            client = new MqttClient(IotEndpoint, 8883, true, caCert, clientCert, MqttSslProtocols.TLSv1_2);

            client.MqttMsgPublishReceived += ClientMqttMsgPublishReceived;
            client.Subscribe(new[] { @"topic_1" }, new[] { MqttMsgBase.QOS_LEVEL_AT_LEAST_ONCE });
            var ret = client.Connect(Guid.NewGuid().ToString());
            Debug.WriteLine("Connected with result code {0}", ret);

            //while (client.IsConnected)
            //{

            //}
        }

        public static void ClientMqttMsgPublishReceived(object sender, MqttMsgPublishEventArgs e)
        {
            var msg = Encoding.UTF8.GetString(e.Message);
            var topic = e.Topic;

            Debug.WriteLine(topic + ", " + msg);

            System.Diagnostics.Process.Start("https://blog.r3it.com/");
        }