IoT Platform:Connect a client to IoT Platform by using the SDK for .NET

Development environment

The following table describes the requirements for the development environment.

Download the SDK

We recommend that you use the AMQP.Net Lite library. To download the library and view its instructions, visit AMQP.Net Lite.

Add the dependency

Add the following dependency to the packages.config file:

<packages>
  <package id="AMQPNetLite" version="2.2.0" targetFramework="net47" />
</packages>

Sample code

using System;
using System.Text;
using Amqp;
using Amqp.Sasl;
using Amqp.Framing;
using System.Threading;
using System.Security.Cryptography.X509Certificates;
using System.Net.Security;
using System.Security.Cryptography;

namespace amqp
{
    class MainClass
    {
        // The endpoint. For more information, see the "Connect an AMQP client to IoT Platform" topic. 
        static string Host = "${YourHost}";
        static int Port = 5671;
        // If you hard-code the AccessKey pair in the project code, the AccessKey pair may be disclosed if the project code is leaked. In this case, the resources within your account become insecure. The following sample code provides an example on how to obtain the AccessKey pair from environment variables. This example is for reference only.
        static string AccessKey = Environment.GetEnvironmentVariable("ALIBABA_CLOUD_ACCESS_KEY_ID");
        static string AccessSecret = Environment.GetEnvironmentVariable("ALIBABA_CLOUD_ACCESS_KEY_SECRET");
        static string consumerGroupId = "${YourConsumerGroupId}";
        static string clientId = "${YourClientId}";
        // iotInstanceId: The ID of the IoT Platform instance. 
        static string iotInstanceId = "${YourIotInstanceId}"; 
        static int Count = 0;
        static int IntervalTime = 10000;

        static Address address;

        public static void Main(string[] args)
        {
            long timestamp = GetCurrentMilliseconds();
            string param = "authId=" + AccessKey + "&timestamp=" + timestamp;
            // The structure of the userName parameter. For more information, see the "Connect an AMQP client to IoT Platform" topic. 
            string userName = clientId + "|authMode=aksign,signMethod=hmacmd5,consumerGroupId=" + consumerGroupId
               + ",iotInstanceId=" + iotInstanceId + ",authId=" + AccessKey + ",timestamp=" + timestamp + "|";
            // Calculate a signature. For more information about how to construct the password, see the "Connect an AMQP client to IoT Platform" topic. 
            string password = doSign(param, AccessSecret, "HmacMD5");

            DoConnectAmqp(userName, password);

            ManualResetEvent resetEvent = new ManualResetEvent(false);
            resetEvent.WaitOne();
        }

        static void DoConnectAmqp(string userName, string password)
        {
            address = new Address(Host, Port, userName, password);
            // Create a connection. 
            ConnectionFactory cf = new ConnectionFactory();
            // Use a local TLS certificate if required. 
            //cf.SSL.ClientCertificates.Add(GetCert());
            //cf.SSL.RemoteCertificateValidationCallback = ValidateServerCertificate;
            cf.SASL.Profile = SaslProfile.External;
            cf.AMQP.IdleTimeout = 120000;
            // Configure the cf.AMQP.ContainerId and cf.AMQP.HostName parameters. 
            cf.AMQP.ContainerId = "client.1.2"; 
            cf.AMQP.HostName = "contoso.com";
            cf.AMQP.MaxFrameSize = 8 * 1024;
            var connection = cf.CreateAsync(address).Result;

            // The connection exception feature is disabled. 
            connection.AddClosedCallback(ConnClosed);

            // Receive messages. 
            DoReceive(connection);
        }

        static void DoReceive(Connection connection)
        {
            // Create a session. 
            var session = new Session(connection);

            // Create a receiver link and receive messages. 
            var receiver = new ReceiverLink(session, "queueName", null);


            receiver.Start(20, (link, message) =>
            {
                object messageId = message.ApplicationProperties["messageId"];
                object topic = message.ApplicationProperties["topic"];
                string body = Encoding.UTF8.GetString((Byte[])message.Body);
                // Note: Do not implement time-consuming logic. If you need to specify the business logic, use a new thread. Otherwise, message consumption may be blocked. Messages may be resent due to the latency of consumption. 
                Console.WriteLine("receive message, topic=" + topic + ", messageId=" + messageId + ", body=" + body);

                // Send an ACK message. 
                link.Accept(message);
            });


        }

        // If an exception occurs, the client attempts to reconnect to IoT Platform. 
        // You can use an exponential backoff algorithm to improve the exception handling mechanism and the reconnection policy. 
        static void ConnClosed(IAmqpObject _, Error e)
        {
            Console.WriteLine("ocurr error: " + e);
            if(Count < 3)
            {
                Count += 1;
                Thread.Sleep(IntervalTime * Count);
            }
            else
            {
                Thread.Sleep(120000);
            }

            // Re-establish the connection. 
            DoConnectAmqp(address.User, address.Password);
        }

        static X509Certificate GetCert()
        {
            string certPath = Environment.CurrentDirectory + "/root.crt";
            X509Certificate crt = new X509Certificate(certPath);

            return crt;
        }

        static bool ValidateServerCertificate(object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors sslPolicyErrors)
        {
            return true;
        }

        static long GetCurrentMilliseconds()
        {
            DateTime dt1970 = new DateTime(1970, 1, 1);
            DateTime current = DateTime.Now;
            return (long)(current - dt1970).TotalMilliseconds;
        }

        // The signature algorithm. Valid values: hmacmd5, hmacsha1, and hmacsha256. 
        static string doSign(string param, string accessSecret, string signMethod)
        {
            //signMethod = HmacMD5
            byte[] key = Encoding.UTF8.GetBytes(accessSecret);
            byte[] signContent = Encoding.UTF8.GetBytes(param);
            var hmac = new HMACMD5(key);
            byte[] hashBytes = hmac.ComputeHash(signContent);
            return Convert.ToBase64String(hashBytes);
        }
    }
}

You can configure the parameters in the preceding code based on the parameter description in the following table. For more information about other parameters, see Connect an AMQP client to IoT Platform.

Sample results

• If information similar to the following output is displayed, the AMQP client is connected to IoT Platform and can receive messages.

  Parameter	Example	Description
  topic	/***********/******/thing/event/property/post	The topic that is used to submit device properties.
  messageId	2**************7	The ID of the message.
  body	{"deviceType":"CustomCategory","iotId":"4EwuVV***","requestId":"161268***","checkFailedData":{},"productKey":"g4***S","gmtCreate":1612682173249,"deviceName":"Esensor","items":{"temperature":{"value":-1,"time":1612682173247},"humidity":{"value":74,"time":1612682173247}}}	The content of the message.

• If information similar to the following output is displayed, the AMQP client fails to connect to IoT Platform.

References

For more information about the error codes that are related to server-side subscription, see Error codes that are related to messages.