MQTT Subscriber Configuration

The subscriber can receive messages from the broker. A payload processing scripts transforms the payloads to HumanOS® internal calls, such as command calls, setting data or properties.

Note: The payload script file (PayloadScriptFile) is mandatory. It is used to transform the payload from other clients into internal calls and sending a corresponding reply.

The following table contains the specific properties of the MQTTClient Subscriber configuration. It extends the general DataLogger subscriber configuration documented in Common DataLogger Configuration.

Parameter	Description	Data Type
Address	IP Address or host name of the message broker	System.String
ServerPort	[OPT] Port of the server. Default ports must not be specified (1883 without TLS & 8883 with TLS)	System.Int32
ClientId	[OPT] Mqtt client id; default is Id of the Publisher	System.String
Username	[OPT] Username	System.String
Password	[OPT] Password of the user.	System.String
Topic	Topic name	System.String
QualityOfService	Quality of Service (QOS)	System.Int32
CleanSession	[OPT] MQTT Clean Session Flag	System.Boolean
ReplyTopic	Reply topic address	System.String
ReplyQualityOfService	Quality of Service for reply channel	System.String
TransportLayerSecurity	[OPT] Security settings for encrypted connection. Possible values are: "None", "Default", "Ssl2", "Ssl3", "Tls", "Tls11", "Tls12"	System.String
IgnoreServerCertificateErrors	[OPT] Flag to ignore certificate errors. Ignores chain errors and name mismatches of server certificate. Default value is false.	System.Boolean
ClientCaCertificateFile	[OPT] Path to client chain certificate for certificate authentication. Requires a ".crt" file. (Is only used for authentication, not for encrypted connection)	System.String
ClientCertificateFile	[OPT] Path to client certificate for certificate authentication. Requires a ".pfx" file (Is only used for authentication, not for encrypted connection)	System.String
ClientCertificatePassword	[OPT] Password for the client certificate	System.String

Subscriber Scripts

The Subscriber scripts are used to parse incoming payloads and to execute functions of the HumanOS® Kernel, such as calling commands, setting data values, ect.

The script object must extend the TAbstractDataConsumerScriptObject<byte[]> class. Following method must be overwritten:

• initialize(): initializes the context of the script. This method is called only once at the beginning.
• processPayload(): Each time a payload is received by the subscription, this method is called.
• postProcess(): After processPayload, this method is called to do some work after successfully processing the payload.

using HumanOS.Kernel;
using HumanOS.Kernel.DataModel;
using HumanOS.Kernel.PeSeL.Script;
using HumanOS.Kernel.Utils;
using Newtonsoft.Json.Linq;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace HumanOS.PeSeL.MQTTClient.Test.HumanOS.PeSeL.MQTTClient
{
  /// <summary>
  /// Implements a simple script to write a temperature limit into node space
  /// </summary>
  public class TDataConsumerScript : TAbstractDataConsumerScriptObject<byte[]>
  {
    ///<see cref="TAbstractDataConsumerScriptObject{T}"/>
    public override void initialize(IKernelAccess Kernel, TPayloadProcessingContext Context)
    {
    }

    ///<see cref="TAbstractDataConsumerScriptObject{T}"/>
    public override void postProcess(IKernelAccess Kernel, TPayloadProcessingContext Context)
    {
    }

    ///<see cref="TAbstractDataConsumerScriptObject{T}"/>
    public override void processPayload(IKernelAccess Kernel, TPayloadProcessingContext Context, byte[] DataReceived, out byte[] oDataToSend)
    {
      oDataToSend = null;

      JObject Obj = JObject.Parse(Encoding.UTF8.GetString(DataReceived));

      string strName = (string)Obj["name"];
      if (strName == "TemperatureLimit")
      {
        INode TempNode = Kernel.NodeSpace.queryNode(n => n.Name == "Temperature");
        TempNode.addProperty<double>("Limit", TValueConverter.convert<double>(Obj["value"]));
        oDataToSend = Encoding.UTF8.GetBytes("Limit Set");
      }
    }
  }
}

Example

{
  "Id": "80E66CB3-9A67-41D0-8F1C-99F95F0ADB8D",
  "Name": "DataNodeSubscriber",
  "PayloadScriptFile": "TDataConsumerScript.cs",
  "SamplingRate": 0.1,
  "Address": "10.196.24.12",
  "Username": "",
  "Password": "",
  "RetainMessages": true,
  "QualityOfService": 2,
  "Topic": "/home/humanos1/in",
  "ReplyTopic": "/home/humanos1/out",
  "ReplyQualityOfService": 2
}