Sample Code for the Cloud .NET SDK

Limits

Prerequisites

• An instance created in the Message Queue for MQTT console.

• A parent topic created in the Message Queue for MQTT console.

• A group created in the Message Queue for MQTT console.

• An AccessKey pair for your Alibaba Cloud account.

Send and receive messages

The following sample code creates one ChannelConfig object and shares it between a consumer and a producer. Three capabilities are demonstrated:

• Message consumption — ServerConsumer.SubscribeTopic subscribes to the parent topic and prints the ID of each message that is received.

• Client status notifications — ServerConsumer.SubscribeStatus subscribes to the online and offline events of the clients in a group and prints the client ID and the event type.

• Message production — ServerProducer.SendMessage publishes a message to topicA/t2 once per second and prints the ID of each message that is sent.

using System.Diagnostics.Tracing;
using System.Text;
using AliyunOnsmqttServerSdk;
using AliyunOnsmqttServerSdk.Common;
using AliyunOnsmqttServerSdk.Config;
using AliyunOnsmqttServerSdk.Model;

class Program
{
    static void Main(string[] args)
    {
        // The cloud endpoint of ApsaraMQ for MQTT.
        string domain = "post-cn-******-server-internet.mqtt.aliyuncs.com";  
        // The instance ID of ApsaraMQ for MQTT.
        string instanceId = "post-cn-******";  
        // The AccessKey ID.
        string ak = "******"; 
        // The AccessKey secret.
        string sk = "******"; 
        // The parent topic.
        string firstTopic = "topicA";
        // The group ID.
        string gid = "GID-test";
        int port = 5672;
        ChannelConfig channelConfig = new ChannelConfig(domain, instanceId, ak, sk, port);
        ServerConsumer serverConsumer = new ServerConsumer(channelConfig);
        serverConsumer.Start();
        // Subscribe to the parent topic.
        serverConsumer.SubscribeTopic(firstTopic,
            (string msgId, MessageProperties messageProperties, byte[] bArr) =>
            {
                Console.WriteLine($"recv:{msgId}");
            });
        // Subscribe to client online and offline events.
        serverConsumer.SubscribeStatus(gid,
            (statusNotice) =>{
                Console.WriteLine($"recv: {statusNotice.ClientId},{statusNotice.EventType}");
            });

        ProducerConfig producerConfig = new ProducerConfig();
        ServerProducer serverProducer = new ServerProducer(channelConfig, producerConfig);
        serverProducer.Start();
        string s = "test";
        Encoding encoding = Encoding.UTF8;
        byte[] payload = encoding.GetBytes(s);
        try
        {
            for(; ; )
            {
                Thread.Sleep(1000);
                SendResult sendResult = serverProducer.SendMessage(firstTopic+"/t2", payload);
                Console.WriteLine($"send: {sendResult.MsgId}");
            }
        }
        catch(Exception e)
        {
            Console.WriteLine(e.StackTrace);
        }

    }
}

Parameters

Endpoints

When you use the cloud SDK to connect to Message Queue for MQTT, specify the endpoint in one of the following formats:

• Public endpoint: <instance ID>-server-internet.mqtt.aliyuncs.com

• VPC endpoint: <instance ID>-server-internal.mqtt.aliyuncs.com

  You can view the instance ID in the Basic Information section of the Instance Details page in the ApsaraMQ for MQTT console.

The sample code in this topic uses the public endpoint format.