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89 lines
3.5 KiB
C#
89 lines
3.5 KiB
C#
// Licensed to the .NET Foundation under one or more agreements.
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// The .NET Foundation licenses this file to you under the MIT license.
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// See the LICENSE file in the project root for more information.
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// ReSharper disable UnusedType.Global
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// ReSharper disable UnusedMember.Global
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// ReSharper disable InconsistentNaming
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using MQTTnet.Client;
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using MQTTnet.Extensions.Rpc;
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using MQTTnet.Protocol;
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namespace MQTTnet.Samples.RpcClient;
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public static class RpcClient_Samples
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{
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/*
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* The extension MQTTnet.Extensions.Rpc (available as nuget) allows sending a request and waiting for the matching reply.
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* This is done via defining a pattern which uses the topic to correlate the request and the response.
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* From client usage it is possible to define a timeout.
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*/
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public static async Task Send_Request()
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{
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var mqttFactory = new MqttFactory();
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// The RPC client is an addon for the existing client. So we need a regular client
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// which is wrapped later.
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using (var mqttClient = mqttFactory.CreateMqttClient())
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{
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var mqttClientOptions = new MqttClientOptionsBuilder()
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.WithTcpServer("broker.hivemq.com")
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.Build();
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await mqttClient.ConnectAsync(mqttClientOptions);
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using (var mqttRpcClient = mqttFactory.CreateMqttRpcClient(mqttClient))
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{
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// Access to a fully featured application message is not supported for RPC calls!
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// The method will throw an exception when the response was not received in time.
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await mqttRpcClient.ExecuteAsync(TimeSpan.FromSeconds(2), "ping", "", MqttQualityOfServiceLevel.AtMostOnce);
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}
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Console.WriteLine("The RPC call was successful.");
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}
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}
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/*
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* The device must respond to the request using the correct topic. The following C code shows how a
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* smart device like an ESP8266 must respond to the above sample.
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*
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// If using the MQTT client PubSubClient it must be ensured
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// that the request topic for each method is subscribed like the following.
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mqttClient.subscribe("MQTTnet.RPC/+/ping");
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mqttClient.subscribe("MQTTnet.RPC/+/do_something");
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// It is not allowed to change the structure of the topic.
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// Otherwise RPC will not work.
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// So method names can be separated using an _ or . but no +, # or /.
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// If it is required to distinguish between devices
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// own rules can be defined like the following:
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mqttClient.subscribe("MQTTnet.RPC/+/deviceA.ping");
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mqttClient.subscribe("MQTTnet.RPC/+/deviceB.ping");
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mqttClient.subscribe("MQTTnet.RPC/+/deviceC.getTemperature");
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// Within the callback of the MQTT client the topic must be checked
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// if it belongs to MQTTnet RPC. The following code shows one
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// possible way of doing this.
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void mqtt_Callback(char *topic, byte *payload, unsigned int payloadLength)
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{
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String topicString = String(topic);
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if (topicString.startsWith("MQTTnet.RPC/")) {
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String responseTopic = topicString + String("/response");
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if (topicString.endsWith("/deviceA.ping")) {
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mqtt_publish(responseTopic, "pong", false);
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return;
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}
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}
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}
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// Important notes:
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// ! Do not send response message with the _retain_ flag set to true.
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// ! All required data for a RPC call and the result must be placed into the payload.
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*/
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}
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