Updates to MQTT

- Added MQTT Protocol support that includes Agent information, a connection heartbeat, and multiple Observation Intervals
- Added QoS configuration parameter for MQTT Client and Relay Agent configurations
- Started adding documentation

applications/Agents/MTConnect-Agent-MQTT-Broker/agent.config.default.yaml

@@ -32,6 +32,12 @@ server: localhost
 # The port number of the MQTT broker to publish messages to
 port: 1883
 
+# The Intervals to publish Observations at (in milliseconds)
+observationIntervals:
+- 0
+- 100
+- 1000
+
 
 # - Agent Configuration -
 

applications/Agents/MTConnect-Agent-MQTT-Relay/agent.config.default.yaml

@@ -32,6 +32,12 @@ server: localhost
 # The port number of the MQTT broker to publish messages to
 port: 1883
 
+# The Intervals to publish Observations at (in milliseconds)
+observationIntervals:
+- 0
+- 100
+- 1000
+
 
 # - Agent Configuration -
 

applications/Clients/MTConnect.NET-Client-MQTT-Example/Program.cs

@@ -1,4 +1,4 @@
-using MTConnect.Clients.Mqtt;
+using MTConnect.Clients;
 using MTConnect.Configurations;
 using MTConnect.Observations;
 
@@ -15,6 +15,8 @@
 var configuration = new MTConnectMqttClientConfiguration();
 configuration.Server = "localhost";
 configuration.Port = 1883;
+//configuration.Interval = 100;
+configuration.DeviceUuid = "OKUMA.Lathe.123456";
 
 var client = new MTConnectMqttClient(configuration, topics: topics);
 client.DeviceReceived += (s, o) =>
@@ -27,7 +29,7 @@
 };
 client.AssetReceived += (s, o) =>
 {
-    Console.WriteLine("Asset Received");
+    Console.WriteLine($"Asset Received : {o.AssetId} : {o.Type}");
 };
 
 await client.StartAsync();

docs/MQTT-Protocol.md

@@ -0,0 +1,55 @@
+# MQTT Protocol for MTConnect
+
+## Overview
+This is a protocol for accessing MTConnect data using MQTT that mimics the functionality of the MTConnect HTTP REST protocol. 
+The main difference between the HTTP and MQTT protocols is that the MQTT protocol deals with the individual MTConnect entities directly (ex. Device, Observation, Asset).
+
+#### All Devices
+![All_Devices](../img/mtconnect-mqtt-protocol-all-01.png)
+
+
+#### By Device
+![All_Devices](../img/mtconnect-mqtt-protocol-by-device-01.png)
+
+
+### Multiple Configurable Observation Intervals
+This protocol enables multiple intervals that Observations can be received. 
+This interval essentially implements a window that a maximum of one Observation per DataItem will be published. 
+This can be used by client applications such as Dashboards. An interval of "0" will indicate that all observation changes are published.
+
+#### Observation Topics
+The interval (in milliseconds) is specified in the brackets suffix for an Observations topic following the pattern below:
+
+##### Observation Interval 1000ms
+```
+MTConnect/Devices/ff8fc5c5-206f-4d94-96a8-a03c70b682b8/Observations[1000]/#
+```
+
+##### Observation Interval 100ms
+```
+MTConnect/Devices/ff8fc5c5-206f-4d94-96a8-a03c70b682b8/Observations[100]/#
+```
+
+##### Observation Interval 0 ("Realtime")
+```
+MTConnect/Devices/ff8fc5c5-206f-4d94-96a8-a03c70b682b8/Observations/#
+```
+
+
+### Agent Connection Heartbeat
+A connection heartbeat that represents the connection between the MTConnect Agent and the MQTT Broker can be read from the topic below:
+```
+MTConnect/Agents/[AGENT_UUID]/HeartbeatTimestamp
+```
+
+The payload is a simple 64 bit Integer representing the last timestamp (in Unix milliseconds) that the Agent sent a heartbeat.
+
+Using this timestamp in combination with the HeartbeatInterval property found in the **MTConnect/Agents/[AGENT_UUID]/Information** topic, 
+the connection status of the MTConnect Agent can be determined. 
+Typically waiting for 3 failed heartbeats allows for temporary connection interruptions and follows a similar pattern of other MTConnect related heartbeat protocols.
+
+
+### Entity level Agent InstanceId support
+Each MTConnect entity contains an InstanceId property which can be compared to the **InstanceId** property found in the **MTConnect/Agents/[AGENT_UUID]/Information**.
+If the entity's InstanceId property differs, then it can be assumed that the Agent was restarted, reconfigured, etc. and the protocol should be restarted.
+This is similar to the MTConnect HTTP protocol.

src/AssemblyInfo.cs

@@ -1,6 +1,6 @@
 using System.Reflection;
 
-[assembly: AssemblyVersion("5.3.0")]
-[assembly: AssemblyFileVersion("5.3.0")]
+[assembly: AssemblyVersion("5.4.0")]
+[assembly: AssemblyFileVersion("5.4.0")]
 [assembly: AssemblyCompany("TrakHound Inc.")]
 [assembly: AssemblyCopyright("Copyright (c) 2023 TrakHound Inc., All Rights Reserved.")]

src/MTConnect.NET-Applications-Agents-MQTT/Configurations/IMqttAgentApplicationConfiguration.cs

@@ -1,12 +1,36 @@
 // Copyright (c) 2023 TrakHound Inc., All Rights Reserved.
 // TrakHound Inc. licenses this file to you under the MIT license.
 
+using System.Collections.Generic;
+
 namespace MTConnect.Configurations
 {
-    public interface IMqttAgentApplicationConfiguration : IAgentApplicationConfiguration, IMTConnectMqttClientConfiguration
+    public interface IMqttAgentApplicationConfiguration : IAgentApplicationConfiguration
     {
+        string Server { get; set; }
+
+        int Port { get; set; }
+
+        string Username { get; set; }
+
+        string Password { get; set; }
+
+        string CertificateAuthority { get; set; }
+
+        string PemCertificate { get; set; }
+
+        string PemPrivateKey { get; set; }
+
+        bool UseTls { get; set; }
+
+        bool AllowUntrustedCertificates { get; set; }
+
+        string TopicPrefix { get; set; }
+
         bool RetainMessages { get; set; }
 
         MTConnectMqttFormat MqttFormat { get; set; }
+
+        IEnumerable<int> ObservationIntervals { get; set; }
     }
 }

src/MTConnect.NET-Applications-Agents-MQTT/Configurations/IMqttRelayAgentApplicationConfiguration.cs

@@ -0,0 +1,14 @@
+// Copyright (c) 2023 TrakHound Inc., All Rights Reserved.
+// TrakHound Inc. licenses this file to you under the MIT license.
+
+namespace MTConnect.Configurations
+{
+    public interface IMqttRelayAgentApplicationConfiguration : IMqttAgentApplicationConfiguration
+    {
+        string ClientId { get; set; }
+
+        int QoS { get; set; }
+
+        int RetryInterval { get; set; }
+    }
+}

src/MTConnect.NET-Applications-Agents-MQTT/Configurations/IShdrMqttRelayAgentApplicationConfiguration.cs

@@ -0,0 +1,13 @@
+// Copyright (c) 2023 TrakHound Inc., All Rights Reserved.
+// TrakHound Inc. licenses this file to you under the MIT license.
+
+namespace MTConnect.Configurations
+{
+    /// <summary>
+    /// Configuration for an MTConnect SHDR > MQTT Agent
+    /// </summary>
+    public interface IShdrMqttRelayAgentApplicationConfiguration : IShdrAgentApplicationConfiguration, IMqttRelayAgentApplicationConfiguration
+    {
+
+    }
+}

src/MTConnect.NET-Applications-Agents-MQTT/Configurations/MqttAgentApplicationConfiguration.cs

@@ -1,6 +1,7 @@
 // Copyright (c) 2023 TrakHound Inc., All Rights Reserved.
 // TrakHound Inc. licenses this file to you under the MIT license.
 
+using System.Collections.Generic;
 using System.Text.Json.Serialization;
 using YamlDotNet.Serialization;
 
@@ -23,9 +24,6 @@ public class MqttAgentApplicationConfiguration : AgentApplicationConfiguration,
         [JsonPropertyName("password")]
         public string Password { get; set; }
 
-        [JsonPropertyName("clientId")]
-        public string ClientId { get; set; }
-
         [JsonPropertyName("certificateAuthority")]
         public string CertificateAuthority { get; set; }
 
@@ -41,9 +39,6 @@ public class MqttAgentApplicationConfiguration : AgentApplicationConfiguration,
         [JsonPropertyName("useTls")]
         public bool UseTls { get; set; }
 
-        [JsonPropertyName("retryInterval")]
-        public int RetryInterval { get; set; }
-
         [JsonPropertyName("retainMessages")]
         public bool RetainMessages { get; set; }
 
@@ -54,14 +49,17 @@ public class MqttAgentApplicationConfiguration : AgentApplicationConfiguration,
         [YamlMember(Alias = "mqttTopicPrefix")]
         public string TopicPrefix { get; set; }
 
+        [JsonPropertyName("observationIntervals")]
+        public IEnumerable<int> ObservationIntervals { get; set; }
+
 
         public MqttAgentApplicationConfiguration()
         {
             Server = "localhost";
             Port = 1883;
-            RetryInterval = 5000;
             RetainMessages = true;
             MqttFormat = MTConnectMqttFormat.Hierarchy;
+            ObservationIntervals = new List<int> { 0, 1000 };
         }
     }
 }

src/MTConnect.NET-Applications-Agents-MQTT/Configurations/MqttRelayAgentApplicationConfiguration.cs

@@ -0,0 +1,30 @@
+// Copyright (c) 2023 TrakHound Inc., All Rights Reserved.
+// TrakHound Inc. licenses this file to you under the MIT license.
+
+using System.Text.Json.Serialization;
+
+namespace MTConnect.Configurations
+{
+    public class MqttRelayAgentApplicationConfiguration : MqttAgentApplicationConfiguration, IMqttRelayAgentApplicationConfiguration
+    {
+        [JsonPropertyName("clientId")]
+        public string ClientId { get; set; }
+
+        [JsonPropertyName("qos")]
+        public int QoS { get; set; }
+
+        [JsonPropertyName("retryInterval")]
+        public int RetryInterval { get; set; }
+
+
+        public MqttRelayAgentApplicationConfiguration()
+        {
+            Server = "localhost";
+            Port = 1883;
+            QoS = 1;
+            RetryInterval = 5000;
+            RetainMessages = true;
+            MqttFormat = MTConnectMqttFormat.Hierarchy;
+        }
+    }
+}

src/MTConnect.NET-Applications-Agents-MQTT/Configurations/MqttRelayAgentGatewayApplicationConfiguration.cs

@@ -0,0 +1,20 @@
+// Copyright (c) 2023 TrakHound Inc., All Rights Reserved.
+// TrakHound Inc. licenses this file to you under the MIT license.
+
+using System.Collections.Generic;
+using System.Text.Json.Serialization;
+
+namespace MTConnect.Configurations
+{
+    /// <summary>
+    /// Configuration for an MTConnect Mqtt Gateway Agent Application
+    /// </summary>
+    public class MqttRelayAgentGatewayApplicationConfiguration : MqttRelayAgentApplicationConfiguration
+    {
+        /// <summary>
+        /// List of MTConnect Http Clients to read from
+        /// </summary>
+        [JsonPropertyName("clients")]
+        public List<HttpClientConfiguration> Clients { get; set; }
+    }
+}

src/MTConnect.NET-Applications-Agents-MQTT/Configurations/ShdrMqttAgentApplicationConfiguration.cs

@@ -1,6 +1,7 @@
 // Copyright (c) 2023 TrakHound Inc., All Rights Reserved.
 // TrakHound Inc. licenses this file to you under the MIT license.
 
+using System.Collections.Generic;
 using System.Text.Json.Serialization;
 using YamlDotNet.Serialization;
 
@@ -23,9 +24,6 @@ public class ShdrMqttAgentApplicationConfiguration : ShdrAgentApplicationConfigu
         [JsonPropertyName("password")]
         public string Password { get; set; }
 
-        [JsonPropertyName("clientId")]
-        public string ClientId { get; set; }
-
         [JsonPropertyName("certificateAuthority")]
         public string CertificateAuthority { get; set; }
 
@@ -41,9 +39,6 @@ public class ShdrMqttAgentApplicationConfiguration : ShdrAgentApplicationConfigu
         [JsonPropertyName("useTls")]
         public bool UseTls { get; set; }
 
-        [JsonPropertyName("retryInterval")]
-        public int RetryInterval { get; set; }
-
         [JsonPropertyName("retainMessages")]
         public bool RetainMessages { get; set; }
 
@@ -54,14 +49,17 @@ public class ShdrMqttAgentApplicationConfiguration : ShdrAgentApplicationConfigu
         [YamlMember(Alias = "mqttTopicPrefix")]
         public string TopicPrefix { get; set; }
 
+        [JsonPropertyName("observationIntervals")]
+        public IEnumerable<int> ObservationIntervals { get; set; }
+
 
         public ShdrMqttAgentApplicationConfiguration()
         {
             Server = "localhost";
             Port = 1883;
-            RetryInterval = 5000;
             RetainMessages = true;
             MqttFormat = MTConnectMqttFormat.Hierarchy;
+            ObservationIntervals = new List<int> { 0, 1000 };
         }
     }
 }