.NET Core Cross-Platform IoT Development: Setting Up Delegate Events (Part 2)

Series Tutorial Directory

 (1) Connect to Alibaba Cloud IOT

 (2) Set Delegate Events

 (3) Report Properties

 (4)  SDK Documentation: Properties, Methods, Delegates, Classes

 http://pan.whuanle.cn/index.php?dir=uploads/阿里云IOT/AliIOTXFclient-dll类库&response

Download the three libraries and include them at the top to use them.

using AliIOTXFClient;

Sample download link

http://pan.whuanle.cn/index.php?dir=uploads/阿里云IOT/demo示例

This chapter's example AliIOTXF.Twe

Lifecycle

Event Types

Currently, five delegate events have been set.

XFMQTT.ConnectionClosedEventHandler 
XFMQTT.PubedEventHandler
XFMQTT.PubEventHandler
XFMQTT.SubedEventHandler
XFMQTT.UnSubedEventHandler

MQTT is a reliable message-pushing protocol, and QOS ensures that messages must be completely pushed to the other side. You can search for specific information about QOS on Baidu~

• QOS = 0, at most once
• QOS = 1, at least once
• QOS = 2, exactly once

This represents the reliability of message pushing. When QOS = 1, under network fluctuations, there may be multiple duplicate push events.

Using Default Delegate Methods:

            // Use default delegate events
            client.UseDefaultEventHandler();

 Through the previous article, the program can now run, connect to the Alibaba Cloud server, and subscribe and publish messages.

These operations will trigger events, and by using the UseDefaultEventHandler() method, the default method is bound to the events.

Custom Event Methods

Remove this line of code.

client.UseDefaultEventHandler();

Include at the top

using uPLibrary.Networking.M2Mqtt.Messages;

Note, the parameters of these five delegate methods are different

XFMQTT.PubEventHandler

Subscription callback - triggered when a message is received from the server

Delegate method is as follows

         Delegate method(object sender, MqttMsgPublishEventArgs e)
        {
    }</span></pre>

MqttMsgPublishEventArgs is an object related to receiving messages, its properties are as follows:

        // message topic
        private string topic;
        // message data
        private byte[] message;
        // duplicate delivery
        private bool dupFlag;
        // quality of service level
        private byte qosLevel;
        // retain flag
        private bool retain;   

The default delegate method provided by the SDK

        public void Default_PubEventHandler(object sender, MqttMsgPublishEventArgs e)
        {
            // handle message received
            string topic = e.Topic;
            string message = Encoding.ASCII.GetString(e.Message);
            Console.WriteLine("- - - - - - - - - - ");
            Console.WriteLine("get topic message, Date: " + DateTime.Now.ToLongTimeString());
            Console.WriteLine("topic: " + topic);
            Console.WriteLine("get message :\n" + message);
        }

Now let's write a custom delegate method

The content inside can be anything, and the method name is arbitrary

        public static void 收到消息(object sender, MqttMsgPublishEventArgs e)
        {
            Console.WriteLine("topic name：" + e.Topic);
            Console.WriteLine("receiving time：" + DateTime.Now.ToLongDateString());
            Console.WriteLine("message content：\n" + Encoding.ASCII.GetString(e.Message));
        }

Add the following in the position where `client.UseDefaultEventHandler();` is deleted

client.PubEventHandler += 收到消息;

XFMQTT.PubedEventHandler

Triggered when subscription is received with QOS=1 or 2

Prototype

Delegate method(object sender, MqttMsgPublishedEventArgs e)
    {
}</span></pre>

MqttMsgPublishedEventArgs Properties

        // message identifier
        ushort messageId;
    </span><span style="color: #008000;">//</span><span style="color: #008000;"> published flag</span>
    <span style="color: #0000ff;">bool</span> isPublished;</pre>

Default method provided by the SDK

        public void Default_PubedEventHandler(object sender, MqttMsgPublishedEventArgs e)
        {
            Console.WriteLine("- - - - - - - - - - ");
            Console.WriteLine("published, Date: " + DateTime.Now.ToLongTimeString());
            Console.WriteLine("MessageId: " + e.MessageId + "    Is Published: " + e.IsPublished);
        }

We will create a custom method, the name can be anything

        public static void 重复收到消息(object sender, MqttMsgPublishedEventArgs e)
        {
            Console.WriteLine("receiving time: " + DateTime.Now.ToLongTimeString());
            Console.WriteLine("message id: " + e.MessageId + "    Is Published: " + e.IsPublished);
        }

Add the following

client.PubedEventHandler += 重复收到消息;

XFMQTT.SubedEventHandler

Triggered when publishing a Topic to the server

Prototype

void 发布消息时(object sender, MqttMsgSubscribedEventArgs e)

MqttMsgSubscribedEventArgs Properties

        /// <summary>
        /// Message identifier
        /// </summary>
        public ushort MessageId {get;set;}
    </span><span style="color: #808080;">///</span> <span style="color: #808080;">&lt;summary&gt;</span>
    <span style="color: #808080;">///</span><span style="color: #008000;"> List of granted QOS Levels
    </span><span style="color: #808080;">///</span> <span style="color: #808080;">&lt;/summary&gt;</span>
    <span style="color: #0000ff;">public</span> <span style="color: #0000ff;">byte</span>[] GrantedQoSLevels {<span style="color: #0000ff;">get</span>;<span style="color: #0000ff;">set</span><span style="color: #000000;">;}

    </span><span style="color: #008000;">//</span><span style="color: #008000;"> message identifier</span>
    <span style="color: #0000ff;">ushort</span><span style="color: #000000;"> messageId;
    </span><span style="color: #008000;">//</span><span style="color: #008000;"> granted QOS levels</span>
    <span style="color: #0000ff;">byte</span>[] grantedQosLevels;</pre>

SDK default implementation

        public void Default_SubedEventHandler(object sender, MqttMsgSubscribedEventArgs e)
        {
            Console.WriteLine("- - - - - - - - - - ");
            Console.WriteLine("Sub topic, Date: " + DateTime.Now.ToLongTimeString());
            Console.WriteLine("MessageId: " + e.MessageId);
            Console.WriteLine("List of granted QOS Levels:    " + string.Join(", " e.GrantedQoSLevels));

Encoding.UTF8.GetString(e.GrantedQoSLevels));
        }</span></pre>
</div>
<p>We write custom code, method names are arbitrary</p>
<div class="cnblogs_code">
<pre>        <span style="color: #0000ff;">public static</span> <span style="color: #0000ff;">void</span> PublishMessage(<span style="color: #0000ff;">object</span><span style="color: #000000;"> sender, MqttMsgSubscribedEventArgs e)
        {
            Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">Message sent to server</span><span style="color: #800000;">"</span><span style="color: #000000;">);
            Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">Send Time: </span><span style="color: #800000;">"</span> +<span style="color: #000000;"> DateTime.Now.ToLongTimeString());
            Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">Message ID: </span><span style="color: #800000;">"</span> +<span style="color: #000000;"> e.MessageId);
            Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">QOS is: </span><span style="color: #800000;">"</span> +<span style="color: #000000;"> Encoding.UTF8.GetString(e.GrantedQoSLevels));
        }</span></pre>
</div>
<p>Add:</p>
<div class="cnblogs_code">
<pre>client.SubscribedEventHandler += PublishMessage;</pre>
</div>
<p>&nbsp;</p>
<h3>XFMQTT.UnsubscribedEventHandler</h3>
<p>Triggered when failing to publish Topic to the server</p>
<div class="cnblogs_code">
<pre><span style="color: #0000ff;">void</span> SendFailure(<span style="color: #0000ff;">object</span><span style="color: #000000;"> sender, MqttMsgUnsubscribedEventArgs )
{

}</span></pre>
</div>
<p>MqttMsgUnsubscribedEventArgs Properties</p>
<div class="cnblogs_code">
<pre>        <span style="color: #808080;">///</span> <span style="color: #808080;">&lt;summary&gt;</span>
        <span style="color: #808080;">///</span><span style="color: #008000;"> Message identifier
        </span><span style="color: #808080;">///</span> <span style="color: #808080;">&lt;/summary&gt;</span>
        <span style="color: #0000ff;">public</span> <span style="color: #0000ff;">ushort</span><span style="color: #000000;"> MessageId
        {
            </span><span style="color: #0000ff;">get</span> { <span style="color: #0000ff;">return</span> <span style="color: #0000ff;">this</span><span style="color: #000000;">.messageId; }
            </span><span style="color: #0000ff;">internal</span> <span style="color: #0000ff;">set</span> { <span style="color: #0000ff;">this</span>.messageId =<span style="color: #000000;"> value; }
        }</span></pre>
</div>
<p>SDK Code</p>
<div class="cnblogs_code">
<pre>        <span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span> Default_UnsubscribedEventHandler(<span style="color: #0000ff;">object</span><span style="color: #000000;"> sender, MqttMsgUnsubscribedEventArgs e)
        {
            Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">- - - - - - - - - - </span><span style="color: #800000;">"</span><span style="color: #000000;">);
            Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">Sub topic error, Date: </span><span style="color: #800000;">"</span> +<span style="color: #000000;"> DateTime.Now.ToLongTimeString());
            Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">MessageId: </span><span style="color: #800000;">"</span> +<span style="color: #000000;"> e.MessageId);
        }</span></pre>
</div>
<p>&nbsp;</p>
<p>We write custom code</p>
<div class="cnblogs_code">
<pre>        <span style="color: #0000ff;">public static</span> <span style="color: #0000ff;">void</span> SendFailure(<span style="color: #0000ff;">object</span><span style="color: #000000;"> sender, MqttMsgUnsubscribedEventArgs e)
        {
            Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">Message send failed </span><span style="color: #800000;">"</span><span style="color: #000000;">);
            Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">Time: </span><span style="color: #800000;">"</span> +<span style="color: #000000;"> DateTime.Now.ToLongTimeString());
            Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">Failed message MessageId: </span><span style="color: #800000;">"</span> +<span style="color: #000000;"> e.MessageId);
        }</span></pre>
</div>
<p>Add:</p>
<div class="cnblogs_code">
<pre>client.UnsubscribedEventHandler += SendFailure;</pre>
</div>
<h3>XFMQTT.ConnectionClosedEventHandler</h3>
<p>Triggered when the connection is closed</p>
<p>&nbsp;SDK Code</p>
<div class="cnblogs_code">
<pre>        <span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span> Default_ConnectionClosedEventHandler(<span style="color: #0000ff;">object</span><span style="color: #000000;"> sender, EventArgs e)
        {
            Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">- - - - - - - - - - </span><span style="color: #800000;">"</span><span style="color: #000000;">);
            Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">Connect Closed error, Date: </span><span style="color: #800000;">"</span> +<span style="color: #000000;"> DateTime.Now.ToLongTimeString());
        }</span></pre>
</div>
<p>Custom code</p>
<div class="cnblogs_code">
<pre>        <span style="color: #0000ff;">public static</span> <span style="color: #0000ff;">void</span> Disconnect(<span style="color: #0000ff;">object</span><span style="color: #000000;"> sender, EventArgs e)
        {
            Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">Date disconnect...</span>

Disconnected: </span><span style="color: #800000;">"</span> +<span style="color: #000000;"> DateTime.Now.ToLongTimeString());
        }</span></pre>
</div>
<p>Add</p>
<div class="cnblogs_code">
<pre>client.ConnectionClosedEventHandler += disconnected;</pre>
</div>
<p>&nbsp;</p>
<p>Complete Code</p>
<div class="cnblogs_code">
<pre>        <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">void</span> Main(<span style="color: #0000ff;">string</span><span style="color: #000000;">[] args)
        {
            </span><span style="color: #008000;">//</span><span style="color: #008000;"> Create connection object</span>
            XFMQTT client = <span style="color: #0000ff;">new</span> XFMQTT(<span style="color: #800000;">"</span><span style="color: #800000;">a1BiPoNawLI</span><span style="color: #800000;">"</span>, <span style="color: #800000;">"</span><span style="color: #800000;">Raspberry</span><span style="color: #800000;">"</span><span style="color: #000000;">);
            </span><span style="color: #008000;">//</span><span style="color: #008000;"> Initialize client configuration</span>
            client.Init(<span style="color: #800000;">"</span><span style="color: #800000;">2NOaBeqXcIzLQEhlJFEfKbWeug0o3m0c</span><span style="color: #800000;">"</span>, <span style="color: #800000;">"</span><span style="color: #800000;">cn-shanghai</span><span style="color: #800000;">"</span><span style="color: #000000;">);
            </span><span style="color: #008000;">//</span><span style="color: #008000;"> Topic to subscribe</span>
            <span style="color: #0000ff;">string</span>[] topic = { client.CombineHeadTopic(<span style="color: #800000;">"</span><span style="color: #800000;">PubData</span><span style="color: #800000;">"</span><span style="color: #000000;">) };

            </span><span style="color: #008000;">//</span><span style="color: #008000;"> Use custom delegate events</span>
            client.PubEventHandler +=<span style="color: #000000;"> messageReceived;
            client.PubedEventHandler </span>+=<span style="color: #000000;"> messageRepeated;
            client.SubedEventHandler </span>+=<span style="color: #000000;"> messagePublished;
            client.UnSubedEventHandler </span>+=<span style="color: #000000;"> sendFailed;
            client.ConnectionClosedEventHandler </span>+=<span style="color: #000000;"> disconnected;
            </span><span style="color: #008000;">//</span><span style="color: #008000;"> Connect to the server</span>
<span style="color: #000000;">            client.ConnectMqtt(topic);

            </span><span style="color: #0000ff;">while</span> (<span style="color: #0000ff;">true</span><span style="color: #000000;">)
            {
                </span><span style="color: #0000ff;">string</span> str =<span style="color: #000000;"> Console.ReadLine();

                </span><span style="color: #008000;">//</span><span style="color: #008000;"> Push content to a specific Topic</span>
                client.Subscribe(client.CombineHeadTopic(<span style="color: #800000;">"</span><span style="color: #800000;">SubData</span><span style="color: #800000;">"</span><span style="color: #000000;">), str);
            }

            Console.ReadKey();
        }
        </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">void</span> messageReceived(<span style="color: #0000ff;">object</span><span style="color: #000000;"> sender, MqttMsgPublishEventArgs e)
        {
            Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">Topic Name:</span><span style="color: #800000;">"</span>+<span style="color: #000000;">e.Topic);
            Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">Receive Time:</span><span style="color: #800000;">"</span> +<span style="color: #000000;"> DateTime.Now.ToLongDateString());
            Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">Message Content:\n</span><span style="color: #800000;">"</span>+<span style="color: #000000;">Encoding.ASCII.GetString(e.Message));
        }
        </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">void</span> messageRepeated(<span style="color: #0000ff;">object</span><span style="color: #000000;"> sender, MqttMsgPublishedEventArgs e)
        {
            Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">Receive Time: </span><span style="color: #800000;">"</span> +<span style="color: #000000;"> DateTime.Now.ToLongTimeString());
            Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">Message ID: </span><span style="color: #800000;">"</span> + e.MessageId + <span style="color: #800000;">"</span><span style="color: #800000;">    Is Published: </span><span style="color: #800000;">"</span> +<span style="color: #000000;"> e.IsPublished);
        }
        </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">void</span> messagePublished(<span style="color: #0000ff;">object</span><span style="color: #000000;"> sender, MqttMsgSubscribedEventArgs e)
        {
            Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">Message Sent to Server</span><span style="color: #800000;">"</span><span style="color: #000000;">);
            Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">Send Time: </span><span style="color: #800000;">"</span> +<span style="color: #000000;"> DateTime.Now.ToLongTimeString());
            Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">Message ID: </span><span style="color: #800000;">"</span> +<span style="color: #000000;"> e.MessageId);
            Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">QOS Level:    </span><span style="color: #800000;">"</span> +<span style="color: #000000;"> Encoding.UTF8.GetString(e.GrantedQoSLevels));
        }
        </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">void</span> sendFailed(<span style="color: #0000ff;">object</span><span style="color: #000000;"> sender, MqttMsgUnsubscribedEventArgs e)
        {
            Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">Message Send Failed </span><span style="color: #800000;">"</span><span style="color: #000000;">);
            Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">Time: </span><span style="color: #800000;">"</span> +<span style="color: #000000;"> DateTime.Now.ToLongTimeString());
            Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">Failed Message MessageId:    </span><span style="color: #800000;">"</span> +<span style="color: #000000;"> e.MessageId);
        }
        </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">void</span> disconnected(<span style="color: #0000ff;">object</span><span style="color: #000000;"> sender, EventArgs e)
        {
            Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">Disconnected...</span><span style="color: #800000;">"</span>);
        }
        </span>

。The connection has been disconnected: " + DateTime.Now.ToLongTimeString());
}