Swarm Space – Underlying Architecture Revisited

After figuring out that calling a CS-Script uplink payload formatter inside an Azure Http Trigger function wasn’t going to work I needed a new architecture.

Swarm Space Azure IoT Connector Identity Translation Gateway Architecture

The new approach uses most of the existing building blocks but adds an Azure HTTP Trigger which receives the Swarm Space Bumble bee hive Webhook Delivery Method calls and writes them to an Azure Storage Queue.

Swarm Space Bumble bee hive Web Hook Delivery method

The uplink and downlink formatters are now called asynchronously so they have limited impact on the overall performance of the application.

Swarm Space – Uplink Payload Startup Problem

I initially noticed a couple of duplicate Swarm Space message PacketIds in Azure IoT Central.

Azure IoT Central with consecutive duplicate PacketIds

Then I started to pay more attention and noticed that duplicate PacketIds could be interleaved

Azure IoT Central with interleaved duplicate PacketIds

Shortly after noticing the interleaved PacketIds I checked the Delivery Method and found there were message delivery timeouts.

Swarm Space Delivery with method timeouts

In Azure Application Insights I could see that the UplinkController was taking up to 15 seconds to execute which was longer than the bumblebee hive delivery timeout.

Azure Application Insights displaying UplinkController metrics.

In Telerik Fiddler I could see calls to the UplinkController taking 16 seconds to execute. (I did see 30+ seconds)

Telerik Fiddler showing duration of Uplink controller calls

To see if the problem was loading CS-Script I added code to load a simple function as the application started. After averaging the duration over many executions there was little difference in the duration.

public interface IApplication
{
    public DateTime Startup(DateTime utcNow);
}
...
protected override async Task ExecuteAsync(CancellationToken cancellationToken)
{
    await Task.Yield();

    _logger.LogInformation("StartUpService.ExecuteAsync start");
            
    // Force the loading and startup of CS Script evaluator
    dynamic application = CSScript.Evaluator
        .LoadCode(
                @"using System;
                public class Application : IApplication
                {
                    public DateTime Startup(DateTime utcNow)
                    {
                        return utcNow;
                    }
                }");

    DateTime result = application.Startup(DateTime.UtcNow);
            
    try
    {
        await _swarmSpaceBumblebeeHive.Login(cancellationToken);

       await _azureIoTDeviceClientCache.Load(cancellationToken);
    }
    catch (Exception ex)
    {
        _logger.LogError(ex, "StartUpService.ExecuteAsync error");

        throw;
    }

    _logger.LogInformation("StartUpService.ExecuteAsync finish");
}

The Swarm Eval Kit uplink formatter (UserApplicationId 65535.cs) “unpacks” the uplink Javascript ObjectNotation(JSON) message, adds an Azure IoT Central compatible location which requires a number of libraries to be loaded.

using System;
using System.Globalization;
using System.Text;

using Microsoft.Azure.Devices.Client;

using Newtonsoft.Json;
using Newtonsoft.Json.Linq;

public class FormatterUplink : PayloadFormatter.IFormatterUplink
{
    public Message Evaluate(int organisationId, int deviceId, int deviceType, int userApplicationId, JObject telemetryEvent, JObject payloadJson, string payloadText, byte[] payloadBytes)
    {
        if ((payloadText != "") && (payloadJson != null))
        {
            JObject location = new JObject();

            location.Add("lat", payloadJson.GetValue("lt"));
            location.Add("lon", payloadJson.GetValue("ln"));
            location.Add("alt", payloadJson.GetValue("a"));

            telemetryEvent.Add("DeviceLocation", location);
        }

        Message ioTHubmessage = new Message(Encoding.ASCII.GetBytes(JsonConvert.SerializeObject(telemetryEvent)));

        ioTHubmessage.Properties.Add("iothub-creation-time-utc", DateTimeOffset.FromUnixTimeSeconds((long)payloadJson.GetValue("d")).ToString("s", CultureInfo.InvariantCulture));

        return ioTHubmessage;
    }
}

I then added code to load the most complex uplink and downlink formatters as the application started. There was a significant reduction in the UplinkController execution durations, but it could still take more than 30 seconds.

try
{
    await _swarmSpaceBumblebeeHive.Login(cancellationToken);

    await _azureIoTDeviceClientCache.Load(cancellationToken);

    await _formatterCache.UplinkGetAsync(65535);

    await _formatterCache.DownlinkGetAsync(20);
}
catch (Exception ex)
{
    _logger.LogError(ex, "StartUpService.ExecuteAsync error");

    throw;
}

I then added detailed telemetry to the code and found that the duration (also variability) was a combination of Azure IoT Device Provisoning Service(DPS) registration, Azure IoT Hub connection establishment, CS-Script payload formatter loading/compilation/execution, application startup tasks and message uploading durations.

After much experimentation It looks like that “synchronously” calling the payload processing code from the Uplink controller is not a viable approach as the Swarm Space Bumblebee hive calls regularly timeout resulting in duplicate messages.

Swarm Space – Uplink Payload Formatters revisited

The approach used in Swarm Space–Uplink Payload Message Creation Time had significant limitations e.g. setting the iothub-creation-time-utc message property.

public interface IFormatterUplink
{
    public Message Evaluate(int organisationId, int deviceId, int deviceType, int userApplicationId, JObject telemetryEvent, JObject payloadJson, string payloadText, byte[] payloadBytes);
}

Uplink payload formatters now return a Microsoft.Azure.Azure.Devices.Client message object to the UplinkController.

...
JObject telemetryEvent = new JObject
{
    { "packetId", payload.PacketId},
    { "deviceType" , payload.DeviceType},
    { "DeviceID", payload.DeviceId },
    { "organizationId", payload.OrganizationId },
    { "UserApplicationId", payload.UserApplicationId},
    { "ReceivedAtUtc", payload.HiveRxTime.ToString("s", CultureInfo.InvariantCulture) },
    { "DataLength", payload.Len },
    { "Data", payload.Data },
    { "Status", payload.Status },
};

    _logger.LogDebug("Uplink-DeviceId:{0} PacketId:{1} TelemetryEvent before:{0}", payload.DeviceId, payload.PacketId, JsonConvert.SerializeObject(telemetryEvent, Formatting.Indented));

    using (Message ioTHubmessage = swarmSpaceFormatterUplink.Evaluate(payload.OrganizationId, payload.DeviceId, context.DeviceType, payload.UserApplicationId, telemetryEvent, payloadJson, payloadText, payloadBytes))
{
    _logger.LogDebug("Uplink-DeviceId:{0} PacketId:{1} TelemetryEvent after:{0}", payload.DeviceId, payload.PacketId, JsonConvert.SerializeObject(telemetryEvent, Formatting.Indented));

    ioTHubmessage.Properties.Add("PacketId", payload.PacketId.ToString());
    ioTHubmessage.Properties.Add("OrganizationId", payload.OrganizationId.ToString());
    ioTHubmessage.Properties.Add("UserApplicationId", payload.UserApplicationId.ToString());
    ioTHubmessage.Properties.Add("DeviceId", payload.DeviceId.ToString());
    ioTHubmessage.Properties.Add("deviceType", payload.DeviceType.ToString());

    await deviceClient.SendEventAsync(ioTHubmessage);

    _logger.LogInformation("Uplink-DeviceID:{deviceId} PacketId:{1} SendEventAsync success", payload.DeviceId, payload.PacketId);
}
...

The default uplink payload formatter (UserApplicationId 0.cs) returns a Microsoft.Azure.Azure.Devices.Client message object with a serialised TelemetryEvent payload.

public class FormatterUplink : PayloadFormatter.IFormatterUplink
{
    public Message Evaluate(int organisationId, int deviceId, int deviceType, int userApplicationId, JObject telemetryEvent, JObject payloadJson, string payloadText, byte[] payloadBytes)
    {
        Message ioTHubmessage = new Message(Encoding.ASCII.GetBytes(JsonConvert.SerializeObject(telemetryEvent)));

        return ioTHubmessage;
    }
}

The Swarm Eval Kit uplink sample formatter (UserApplicationId 65535.cs) “unpacks” the uplink Javascript ObjectNotation(JSON) message, adds an Azure IoT Central compatible location to the TelemetryEvent and an “iothub-creation-time-utc” message property.

public class FormatterUplink : PayloadFormatter.IFormatterUplink
{
    public Message Evaluate(int organisationId, int deviceId, int deviceType, int userApplicationId, JObject telemetryEvent, JObject payloadJson, string payloadText, byte[] payloadBytes)
    {
        if ((payloadText != "") && (payloadJson != null))
        {
            JObject location = new JObject();

            location.Add("lat", payloadJson.GetValue("lt"));
            location.Add("lon", payloadJson.GetValue("ln"));
            location.Add("alt", payloadJson.GetValue("a"));

            telemetryEvent.Add("DeviceLocation", location);
        }

        Message ioTHubmessage = new Message(Encoding.ASCII.GetBytes(JsonConvert.SerializeObject(telemetryEvent)));

        ioTHubmessage.Properties.Add("iothub-creation-time-utc", DateTimeOffset.FromUnixTimeSeconds((long)payloadJson.GetValue("d")).ToString("s", CultureInfo.InvariantCulture));

        return ioTHubmessage;
    }
}

If the uplink formatter compilation or execution fails, a detailed exception message is logged to Azure Application Insights

Detailed compilation error message in Application Insights

I need to add some tools to make the creation, modification, deletion and debugging of downlink/uplink formatters easier.

Swarm Space – Uplink Payload Message Creation Time

The Swarm Space satellite constellation doesn’t have continuous coverage (Jan 2023) so messages sent when there is no coverage are queued (default 48hrs) by the Swarm M138 Modem for transmission when a satellite passes overhead.

Satellite Passes with gap in coverage from 16:18 to 18:42 highlighted

In the Swarm Hive Delivery Method messages from the Swarm Eval Kit and Swarm Tracker in my backyard arriving in “clusters”.

Swarm Hive Delivery Methods webhook calls.

The messages in each “cluster” were processed by a payload formatter then forwarded to Azure IoT Central for processing. All the messages in a cluster had similar event creation times which was “breaking” graphs and device tracking maps. After running the application locally using Telerik Fiddler to try different payloads I realised that the Microsoft.Azure.Azure.Devices.Client message iothub-creation-time-utc property was set to the when the message was received by Swarm Space infrastructure.

_logger.LogDebug("Uplink-DeviceId:{0} PacketId:{1} TelemetryEvent before:{0}", payload.DeviceId, payload.PacketId, JsonConvert.SerializeObject(telemetryEvent, Formatting.Indented));

telemetryEvent = swarmSpaceFormatterUplink.Evaluate(telemetryEvent, payload.Data, payloadBytes, payloadText, payloadJson);

_logger.LogDebug("Uplink-DeviceId:{0} PacketId:{1} TelemetryEvent after:{0}", payload.DeviceId, payload.PacketId, JsonConvert.SerializeObject(telemetryEvent, Formatting.Indented));

// Send the message to Azure IoT Hub
using (Message ioTHubmessage = new Message(Encoding.ASCII.GetBytes(JsonConvert.SerializeObject(telemetryEvent))))
{
   // Ensure the displayed time is the acquired time rather than the uploaded time. 
   ioTHubmessage.Properties.Add("iothub-creation-time-utc", payload.HiveRxTime.ToString("s", CultureInfo.InvariantCulture));
   ioTHubmessage.Properties.Add("PacketId", payload.PacketId.ToString());
   ioTHubmessage.Properties.Add("OrganizationId", payload.OrganizationId.ToString());
   ioTHubmessage.Properties.Add("ApplicationId", payload.UserApplicationId.ToString());
   ioTHubmessage.Properties.Add("DeviceId", payload.DeviceId.ToString());
   ioTHubmessage.Properties.Add("deviceType", payload.DeviceType.ToString());

   await deviceClient.SendEventAsync(ioTHubmessage);

   _logger.LogInformation("Uplink-DeviceID:{deviceId} SendEventAsync success", payload.DeviceId);
}

The Swarm Eval Kit uplink (JSON) message generated by the sample firmware “d” field is the number of seconds since the Unix Epoch that the message payload was constructed.

Swarm Hive Messages with “d” field in the JSON payload highlighted
Online Unix Epoch Convertor displaying Unix Epoch 1672561286 in NZDT and UTC time

The revised 65355.cs payload formatter adds an “iothub-creation-time-utc” field to the TelemetryEvent

using System;
using System.Globalization;

using Newtonsoft.Json.Linq;

public class FormatterUplink : PayloadFormatter.IFormatterUplink
{
    public JObject Evaluate(JObject telemetryEvent, string payloadBase64, byte[] payloadBytes, string payloadText, JObject payloadJson)
    {
        if ((payloadText != "" ) && ( payloadJson != null))
        {
            JObject location = new JObject();

            location.Add("lat", payloadJson.GetValue("lt"));
            location.Add("lon", payloadJson.GetValue("ln"));
            location.Add("alt", payloadJson.GetValue("a"));

            telemetryEvent.Add("DeviceLocation", location);
        };

        telemetryEvent.Add("iothub-creation-time-utc", DateTimeOffset.FromUnixTimeSeconds((long)payloadJson.GetValue("d")).ToString("s", CultureInfo.InvariantCulture));

        return telemetryEvent;
    }
}

Which, if present is used to populate theMicrosoft.Azure.Azure.Devices.Client message iothub-creation-time-utc property

_logger.LogDebug("Uplink-DeviceId:{0} PacketId:{1} TelemetryEvent before:{0}", payload.DeviceId, payload.PacketId, JsonConvert.SerializeObject(telemetryEvent, Formatting.Indented));

telemetryEvent = swarmSpaceFormatterUplink.Evaluate(telemetryEvent, payload.Data, payloadBytes, payloadText, payloadJson);

.LogDebug("Uplink-DeviceId:{0} PacketId:{1} TelemetryEvent after:{0}", payload.DeviceId, payload.PacketId, JsonConvert.SerializeObject(telemetryEvent, Formatting.Indented));

Send the message to Azure IoT Hub
using (Message ioTHubmessage = new Message(Encoding.ASCII.GetBytes(JsonConvert.SerializeObject(telemetryEvent))))
{
   // Ensure the displayed time is the acquired time rather than the uploaded time. 
   ioTHubmessage.Properties.Add("PacketId", payload.PacketId.ToString());
   ioTHubmessage.Properties.Add("OrganizationId", payload.OrganizationId.ToString());
   ioTHubmessage.Properties.Add("UserApplicationId", payload.UserApplicationId.ToString());
   ioTHubmessage.Properties.Add("DeviceId", payload.DeviceId.ToString());
   ioTHubmessage.Properties.Add("deviceType", payload.DeviceType.ToString());

   if (telemetryEvent.ContainsKey("iothub-creation-time-utc"))
   {
      ioTHubmessage.Properties.Add("iothub-creation-time-utc",telemetryEvent.Value<string>("iothub-creation-time-utc"));
   }

   await deviceClient.SendEventAsync(ioTHubmessage);

   _logger.LogInformation("Uplink-DeviceID:{deviceId} SendEventAsync success", payload.DeviceId);
}

The Azure IoT Central message now had the correct timestamp and “event creation time” values.

AzureIoT Central “Raw Data” with valid timestamp and event creation times

I don’t think this is a good solution

The design of the payload formatters will have to be revisited

Swarm Space – Uplink Payload formatter caching and files

The payload formatters of my Azure IoT Hub Cloud Identity Translation Gateway use CS-Script and even a simple one was taking more than half a second to compile each time it was called.

using System;
using System.Globalization;

using Newtonsoft.Json.Linq;

public class FormatterUplink : PayloadFormatter.IFormatterUplink
{
    public JObject Evaluate(JObject telemetryEvent, string payloadBase64, byte[] payloadBytes, string payloadText, JObject payloadJson)
    {
        if ((payloadText != "" ) && ( payloadJson != null))
        {
            JObject location = new JObject();

            location.Add("lat", payloadJson.GetValue("lt"));
            location.Add("lon", payloadJson.GetValue("ln"));
            location.Add("alt", payloadJson.GetValue("a"));

            telemetryEvent.Add("Location", location);
        };

        return telemetryEvent;
    }
}

The Swarm Eval Kit default message has a userApplicationId of 65335

{"ln":123.456,"si":0.0,"bi":0.2,"sv":0.152,"lt":-12.345,"bv":4.032,"d":1671704370,"n":2,"a":9.0,"s":1.0,"c":208.0,"r":-94,"ti":0.032}

The 65355.cs payload formatter adds an Azure IoT Central compatible location to the telemetry payload.

Azure IoT Central uplink telemetry message payload

The formatter files are currently part of the SwarmSpaceAzureIoTConnector project (moving to Azure Blob Storage) so are configured as “content” (bonus syntax highlighting works) and “copy if newer” so they are included in the deployment package.

Visual Studio 2022 Sample payload formatter

I used Alastair Crabtrees’s LazyCache to store compiled payload formatters with Uplink/Downlink + UserApplicationId as the cache key.

public class FormatterCache : IFormatterCache
{
    private readonly ILogger<FormatterCache> _logger;
    private readonly Models.ApplicationSettings _applicationSettings;
    private readonly static IAppCache _payloadFormatters = new CachingService();

    public FormatterCache(ILogger<FormatterCache>logger, IOptions<Models.ApplicationSettings> applicationSettings)
    {
        _logger = logger;
        _applicationSettings = applicationSettings.Value;
    }

    public async Task<IFormatterUplink> UplinkGetAsync(int userApplicationId)
    {
        IFormatterUplink payloadFormatterUplink = await _payloadFormatters.GetOrAddAsync<PayloadFormatter.IFormatterUplink>($"U{userApplicationId}", (ICacheEntry x) => UplinkLoadAsync(userApplicationId), memoryCacheEntryOptions);

        return payloadFormatterUplink;
    }

    private async Task<IFormatterUplink> UplinkLoadAsync(int userApplicationId)
    {
        string payloadformatterFilePath = $"{_applicationSettings.PayloadFormattersUplinkFilePath}\\{userApplicationId}.cs";

        if (!File.Exists(payloadformatterFilePath))
        {
            _logger.LogInformation("PayloadFormatterUplink- UserApplicationId:{0} PayloadFormatterPath:{1} not found using default:{2}", userApplicationId, payloadformatterFilePath, _applicationSettings.PayloadFormatterUplinkDefault);

            return CSScript.Evaluator.LoadFile<PayloadFormatter.IFormatterUplink>(_applicationSettings.PayloadFormatterUplinkDefault);
        }

        _logger.LogInformation("PayloadFormatterUplink- UserApplicationId:{0} loading PayloadFormatterPath:{1}", userApplicationId, payloadformatterFilePath);

        return CSScript.Evaluator.LoadFile<PayloadFormatter.IFormatterUplink>(payloadformatterFilePath);
    }
...
}

The default uplink and downlink formatters are configured in application settings and are used when a UserApplicationId specific formatter is not configured.

Fiddler Composer illustrating compiled formatter timings before and after caching

Swarm Space – Uplink Payload formatter Proof of Concept(PoC)

My Azure IoT Hub Cloud Identity Translation Gateway will support the translation of Base64 encoded uplink payloads to Javascript Object Notation (JSON) so they can be processed by Azure IoT Hub client applications and Azure IoT Central. This PoC uses CS-Script by Oleg Shilo to transform the Swarm Eval Kit Base64 encoded JSON uplink messages.

Swarm Hive message list with a message payload

A sample decoded (JSON) Swarm Eval Kit uplink message

{"ln":123.456,"si":0.0,"bi":0.2,"sv":0.152,"lt":-12.345,"bv":4.032,"d":1671704370,"n":2,"a":9.0,"s":1.0,"c":208.0,"r":-94,"ti":0.032}

A Webhook Delivery method forwards uplink messages to my Azure IoT Hub Cloud Identity Translation Gateway.

Swarm Hive Delivery configuration with recent uplink messages

My first hard-coded payload formatter adds an Azure IoT Central compatible location to the telemetry event payload.

const string codeSwarmSpaceUplinkFormatterCode = @"
   using Newtonsoft.Json.Linq;

   public class UplinkFormatter : PayloadFormatter.ISwarmSpaceFormatterUplink
   {
       public JObject Evaluate(JObject telemetryEvent, string payloadBase64, byte[] payloadBytes, string payloadText, JObject payloadJson)
       {
           if ((payloadText != """" ) && ( payloadJson != null))
           {
               JObject location = new JObject() ;

               location.Add(""Lat"", payloadJson.GetValue(""lt""));
               location.Add(""Lon"", payloadJson.GetValue(""ln""));
               location.Add(""Alt"", payloadJson.GetValue(""a""));

               telemetryEvent.Add( ""location"", location);
           };

           return telemetryEvent;
       }
   }";
}

The PayloadFormatter namespace was added to reduce the length of the payload formatter C# interface declarations.

namespace PayloadFormatter 
{
    using Newtonsoft.Json.Linq;

    public interface ISwarmSpaceFormatterUplink
    {
        public JObject Evaluate(JObject telemetry, string payloadBase64, byte[] payloadBytes, string payloadText, JObject payloadJson);
    }

    public interface ISwarmSpaceFormatterDownlink
    {
        public string Evaluate(JObject payloadJson, string payloadText, byte[] payloadBytes, string payloadBase64);
    }
}

namespace devMobile.IoT.SwarmSpace.AzureIoT.Connector
{
    using System.Threading.Tasks;
    using Microsoft.Extensions.Logging;

    using CSScriptLib;

    using PayloadFormatter;

    public interface ISwarmSpaceFormatterCache
    {
        public Task<ISwarmSpaceFormatterUplink> PayloadFormatterGetOrAddAsync(int userApplicationId);

    }

    public class SwarmSpaceFormatterCache : ISwarmSpaceFormatterCache
    {
        private readonly ILogger<SwarmSpaceFormatterCache> _logger;

        public SwarmSpaceFormatterCache(ILogger<SwarmSpaceFormatterCache>logger)
        {
            _logger = logger;
        }

        public async Task<ISwarmSpaceFormatterUplink> PayloadFormatterGetOrAddAsync(int deviceId)
        {
            return CSScript.Evaluator.LoadCode<PayloadFormatter.ISwarmSpaceFormatterUplink>(codeSwarmSpaceUplinkFormatterCode);
        }
...
}

The parameters of the formatter are Base64 encoded, textual and a Newtonsoft JObject representations of the uplink payload and a telemetry event populated with some uplink message metadata.

Azure IoT Central uplink telemetry message payload

The initial “compile” of an uplink formatter was taking approximately 2.1 seconds so they will be “compiled” on demand and cached in a Dictionary with the UserApplicationId as the key. A default uplink formatter will be used when a UserApplicationId specific uplink formatter is not configured.

Swarm Space – Azure IoT FromDevice with webhooks

The initial versions of the Swarm Space Azure Cloud Identity Gateway were based on my The Things Industries(TTI) Azure IoT Connector which used six HTTP Triggered Azure Functions. My Swarm Space Azure IoT connector only has one webhook endpoint so a .NET Core WebAPI with controllers based solution appeared to be more practical. The first step was to get some sample JavaScript Object Notation(JSON) uplink message payloads with the SwarmSpace-From Device with Webhooks project.

{
  "packetId": 0,
  "deviceType": 1,
  "deviceId": 0,
  "userApplicationId": 0,
  "organizationId": 65760,
  "data": "VGhpcyBpcyBhIHRlc3QgbWVzc2FnZS4gVGhlIHBhY2tldElkIGFuZCBkZXZpY2VJZCBhcmUgbm90IHBvcHVsYXRlZCwgYnV0IHdpbGwgYmUgZm9yIGEgcmVhbCBtZXNzYWdlLg==",
  "len": 100,
  "status": 0,
  "hiveRxTime": "2022-11-29T04:52:06"
}

I used JSON2CSharp to generate an initial version of a Plain Old CLR(ComonLanguage Runtime) Object(POCO) to deserialise the Delivery Webhook payload.

 https://json2csharp.com/
    
    // Root myDeserializedClass = JsonConvert.DeserializeObject<Root>(myJsonResponse);
    public class Root
    {
        public int packetId { get; set; }
        public int deviceType { get; set; }
        public int deviceId { get; set; }
        public int userApplicationId { get; set; }
        public int organizationId { get; set; }
        public string data { get; set; }
        public int len { get; set; }
        public int status { get; set; }
        public DateTime hiveRxTime { get; set; }
    }
*/

I then “tweaked” the JSON2CSharp class

 public class UplinkPayload
    {
        [JsonProperty("packetId")]
        public int PacketId { get; set; }

        [JsonProperty("deviceType")]
        public int DeviceType { get; set; }

        [JsonProperty("deviceId")]
        public int DeviceId { get; set; }

        [JsonProperty("userApplicationId")]
        public int UserApplicationId { get; set; }

        [JsonProperty("organizationId")]
        public int OrganizationId { get; set; }

        [JsonProperty("data")]
        [JsonRequired]
        public string Data { get; set; }

        [JsonProperty("len")]
        public int Len { get; set; }

        [JsonProperty("status")]
        public int Status { get; set; }

        [JsonProperty("hiveRxTime")]
        public DateTime HiveRxTime { get; set; }
    }

This class is used to “automagically” deserialise Delivery Webhook payloads. There is also some additional payload validation which discards test messages (not certain this is a good idea) etc.

//---------------------------------------------------------------------------------
// Copyright (c) December 2022, devMobile Software
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
//---------------------------------------------------------------------------------
namespace devMobile.IoT.SwarmSpace.AzureIoT.Connector.Controllers
{
    using System.Globalization;
    using System.Text;
    using System.Threading.Tasks;

    using Microsoft.AspNetCore.Mvc;
    using Microsoft.Azure.Devices.Client;
    using Microsoft.Extensions.Logging;

    using Newtonsoft.Json;
    using Newtonsoft.Json.Linq;

    [ApiController]
    [Route("api/[controller]")]
    public class UplinkController : ControllerBase
    {
        private readonly ILogger<UplinkController> _logger;
        private readonly IAzureIoTDeviceClientCache _azureIoTDeviceClientCache;

        public UplinkController(ILogger<UplinkController> logger, IAzureIoTDeviceClientCache azureIoTDeviceClientCache)
        {
            _logger = logger;
            _azureIoTDeviceClientCache = azureIoTDeviceClientCache;
        }

        [HttpPost]
        public async Task<IActionResult> Uplink([FromBody] Models.UplinkPayload payload)
        {
            DeviceClient deviceClient;

            _logger.LogDebug("Payload {0}", JsonConvert.SerializeObject(payload, Formatting.Indented));

            if (payload.PacketId == 0)
            {
                _logger.LogWarning("Uplink-payload simulated DeviceId:{DeviceId}", payload.DeviceId);

                return this.Ok();
            }

            if ((payload.UserApplicationId < Constants.UserApplicationIdMinimum) || (payload.UserApplicationId > Constants.UserApplicationIdMaximum))
            {
                _logger.LogWarning("Uplink-payload invalid User Application Id:{UserApplicationId}", payload.UserApplicationId);

                return this.BadRequest($"Invalid User Application Id {payload.UserApplicationId}");
            }

            if ((payload.Len < Constants.PayloadLengthMinimum) || string.IsNullOrEmpty(payload.Data))
            {
                _logger.LogWarning("Uplink-payload.Data is empty PacketId:{PacketId}", payload.PacketId);

                return this.Ok("payload.Data is empty");
            }

            Models.AzureIoTDeviceClientContext context = new Models.AzureIoTDeviceClientContext()
            {
                OrganisationId = payload.OrganizationId,
                UserApplicationId = payload.UserApplicationId,
                DeviceType = payload.DeviceType,
                DeviceId = payload.DeviceId,
            };

            deviceClient = await _azureIoTDeviceClientCache.GetOrAddAsync(payload.DeviceId.ToString(), context);

            JObject telemetryEvent = new JObject
            {
                { "packetId", payload.PacketId},
                { "deviceType" , payload.DeviceType},
                { "DeviceID", payload.DeviceId },
                { "organizationId", payload.OrganizationId },
                { "ApplicationId", payload.UserApplicationId},
                { "ReceivedAtUtc", payload.HiveRxTime.ToString("s", CultureInfo.InvariantCulture) },
                { "DataLength", payload.Len },
                { "Data", payload.Data },
                { "Status", payload.Status },
            };

            // Send the message to Azure IoT Hub
            using (Message ioTHubmessage = new Message(Encoding.ASCII.GetBytes(JsonConvert.SerializeObject(telemetryEvent))))
            {
                // Ensure the displayed time is the acquired time rather than the uploaded time. 
                ioTHubmessage.Properties.Add("iothub-creation-time-utc", payload.HiveRxTime.ToString("s", CultureInfo.InvariantCulture));
                ioTHubmessage.Properties.Add("OrganizationId", payload.OrganizationId.ToString());
                ioTHubmessage.Properties.Add("ApplicationId", payload.UserApplicationId.ToString());
                ioTHubmessage.Properties.Add("DeviceId", payload.DeviceId.ToString());
                ioTHubmessage.Properties.Add("deviceType", payload.DeviceType.ToString());

                await deviceClient.SendEventAsync(ioTHubmessage);

                _logger.LogInformation("Uplink-DeviceID:{deviceId} SendEventAsync success", payload.DeviceId);
            }

            return this.Ok();
        }
    }
}

I initially debugged and tested the Uplink controller with Telerik Fiddler using sample payloads captured with the SwarmSpace-From Device with Webhooks project.

Using Telerik Fiddler to make test delivery webhook calls

Which I could then inspect with Azure IoT Explorer as they arrived

Azure IoT Explorer displaying a test message

The next step was to create a new Delivery Method

Swarm delivery webhook creation

Configured to call my Uplink controller endpoint.

Swarm delivery webhook configuration

The webhook was configured to “acknowledge messages on successful delivery”. I then checked my Delivery Method configuration with a couple of “Test” messages.

My Swarm Space Eval Kit arrived md-week and after some issues with jumper settings it started reporting position and status information.

Swarm Eval Kit in my backyard

The first position was just of the coast of West Africa(null island)

Swarm Map centered on Null Island

After the Global Positioning System(GPS) receiver got a good fix the location of the Eval Kit was in the middle of my backyard.

Azure IoT Explorer displaying payload with good latitude and longitude
Swarm Map displaying the location of my device (zoomed out)

Swarm Space – Payload formatters with CS-Script

My Azure IoT Hub Cloud Identity Translation Gateway needs to support the translation of Base64 encoded uplink payloads to Javascript Object Notation (JSON) and downlink payloads to Base64 encoded from Javascript Object Notation (JSON) . This so uplink and downlink messages can be processed and generated by Azure IoT Hub connected and Azure IoT Central applications.

To format uplink and downlink messages I had been looking at CS-Script by Oleg Shilo which is a Common Language Runtime(CLR) based scripting system that uses European Computer Manufacturers Association (ECMA)-compliant C# as a programming language.

I started with a modified version of the first sample on Github.

public class Samples
{
    const string codeMethod = @"
        int Multiply(int a, int b)
        {
            return a * b;
        }";

    public void Execute1()
    {
       dynamic script = CSScript.Evaluator.LoadMethod(codeMethod);

        int result = script.Multiply(3, 2);

        Console.WriteLine($"Product 1:{result}");
    }
...
internal class Program
{
    static void Main(string[] args)
    {
        new Samples().Execute1();
...
        Console.WriteLine($"Press Enter to exit");
        Console.ReadLine();
    }
}

I then modified it to use a C# interface and the application failed with an exception

CSScriptLib.CompilerException
  HResult=0x80131600
  Message=(2,39): error CS0246: The type or namespace name 'IMultiplier' could not be found (are you missing a using directive or an assembly reference?)

  Source=CSScriptLib
  StackTrace:
   at CSScriptLib.RoslynEvaluator.Compile(String scriptText, String scriptFile, CompileInfo info)
   at CSScriptLib.EvaluatorBase`1.LoadCode[T](String scriptText, Object[] args)
   at devMobile.IoT.SwarmSpace.AzureIoT.PayloadFormatterCSScript.Samples.Execute2A() in C:\Users\BrynLewis\source\repos\SwarmSpaceAzureIoT\PayloadFormatterCSScipt\Program.cs:line 90
   at devMobile.IoT.SwarmSpace.AzureIoT.PayloadFormatterCSScript.Program.Main(String[] args) in C:\Users\BrynLewis\source\repos\SwarmSpaceAzureIoT\PayloadFormatterCSScipt\Program.cs:line 375

After some trial and error, I figured out I had the namespace wrong

const string codeClassA = @"
    public class Calculator : devMobile.IoT.SwarmSpace.AzureIoT.PayloadFormatterCSScript.IMultiplier
    {
        public int Multiply(int a, int b)
        {

            return a * b;
        }
    }";

public void Execute2A()
{
    IMultiplier multiplierA = CSScript.Evaluator.LoadCode<IMultiplier>(codeClassA);

    Console.WriteLine($"Product 2A:{multiplierA.Multiply(3, 2)} - Press Enter to exit");
}

The long namespace would have been a pain in the arse (PITA) for users creating payload formatters and after some experimentation I added another interface with a short namespace. (Not certain this is a good idea).

namespace PayloadFormatter // Additional namespace for shortening interface for formatters
{
    public interface IMultiplier
    {
        int Multiply(int a, int b);
    }
}
...
public void Execute2B()
{
      PayloadFormatter.IMultiplier multiplierB = CSScript.Evaluator.LoadCode<PayloadFormatter.IMultiplier>(codeClassB);

     Console.WriteLine($"Product 2B:{multiplierB.Multiply(3, 2)} - Press Enter to exit");
}

I then wanted to figure out how to limit the namepaces the script has access to

const string codeClassDebug = @"
    using System.Diagnostics;

    public class Calculator : devMobile.IoT.SwarmSpace.AzureIoT.PayloadFormatterCSScript.IMultiplier
    {
        public int Multiply(int a, int b)
        {
           Debug.WriteLine(""Oops""); // Comment out the using System.Diagnostics;

            return a * b;
        }
    }";

public void Execute3()
{
    CSScript.Evaluator.Reset(true);

    IMultiplier multiplier = CSScript.Evaluator
        .LoadCode<IMultiplier>(codeClassDebug);

    int result = multiplier.Multiply(6, 2);

    Console.WriteLine($"Product 3:{result}");
}

The CSScript.Evaluator.Reset(true); removes all of the “default” references but a using directive could make namespaces available, so this needs some more investigation

The next step was to build the simplest possible payload formatter a “pipe” which displayed the text encoded in Base64 string.

const string codeSwarmSpaceFormatterPipe = @"
    public class SwarmSpaceFormatter:devMobile.IoT.SwarmSpace.AzureIoT.PayloadFormatterCSScript.ISwarmSpaceFormatterPipe
    {
        public string Pipe(string payloadBase64)
        {
            var payloadBase64Bytes = System.Convert.FromBase64String(payloadBase64);

             return System.Text.Encoding.UTF8.GetString(payloadBase64Bytes);
        }
    }";
...
public void Execute4()
{
    ISwarmSpaceFormatterPipe SwarmSpaceFormatter = CSScript.Evaluator
           ...
                        .LoadCode<ISwarmSpaceFormatterPipe>(codeSwarmSpaceFormatterPipe);

    string payload = SwarmSpaceFormatter.Pipe(PayloadBase64);

    Console.WriteLine($"Pipe:{payload}");
}

The Base64 encoded uplink payloads will have to be converted to JSON and the downlink JSON payloads will have to be converted to Base64 encoded binary, so I created an uplink and downlink formatters.

public void Execute5()
{
    string namespaces = $"using Newtonsoft.Json.Linq;using System;\n";
    string code = namespaces + codeSwarmSpaceFormatter;

    JObject telemetry = new JObject
    {
            { "ApplicationID", 12345 },
            { "DeviceID", 54321 },
            { "DeviceType", 2 },
            { "ReceivedAtUtc", DateTime.UtcNow.ToString("s", CultureInfo.InvariantCulture) },
    };

    ISwarmSpaceFormatter SwarmSpaceFormatter = CSScript.Evaluator.LoadCode<ISwarmSpaceFormatter>(code);

    string pipePayload = SwarmSpaceFormatter.Pipe(PayloadBase64);

    Console.WriteLine($"Pipe:{pipePayload}");
    Console.WriteLine("");


    JObject uplinkPayload = SwarmSpaceFormatter.Uplink(telemetry, PayloadBase64, Convert.FromBase64String(PayloadBase64));

    Console.WriteLine($"Uplink:{uplinkPayload}");
    Console.WriteLine("");

    JObject command = new JObject
    {
        {"Temperature", 1},
    };

    string downlinkPayload = SwarmSpaceFormatter.Downlink(command);

    Console.WriteLine($"Downlink:{downlinkPayload}");
    Console.WriteLine("");
}

I found that having both the byte array and Base64 encoded representation of the uplink payloads was useful. The first formatter converts the temperature field of the downlink payload into a four byte array then reverses the array to illustrate how packed byte payloads could be constructed.

const string codeSwarmSpaceFormatter1 = @"
    public class SwarmSpaceFormatter : devMobile.IoT.SwarmSpace.AzureIoT.PayloadFormatterCSScript.ISwarmSpaceFormatter
    {
        public string Pipe(string payloadBase64)
        {
            var payloadBase64Bytes = System.Convert.FromBase64String(payloadBase64);

            return System.Text.Encoding.UTF8.GetString(payloadBase64Bytes);
       }

        public JObject Uplink(JObject telemetryEvent, string payloadBase64, byte[] payloadBytes)
        {
            var payloadBase64Bytes = System.Convert.FromBase64String(payloadBase64);

            telemetryEvent.Add(""PayloadBase64"", payloadBase64Bytes);
            telemetryEvent.Add(""PayloadBytes"",System.Text.Encoding.UTF8.GetString(payloadBytes));

            return telemetryEvent;
        }

        public string Downlink(JObject command)
        {
            int temperature = command.Value<int>(""Temperature"");

            return System.Convert.ToBase64String(BitConverter.GetBytes(temperature));
        }
    }";

const string codeSwarmSpaceFormatter2 = @"
    public class SwarmSpaceFormatter:devMobile.IoT.SwarmSpace.AzureIoT.PayloadFormatterCSScript.ISwarmSpaceFormatter
    {
        public string Pipe(string payloadBase64)
        {
            var payloadBase64Bytes = System.Convert.FromBase64String(payloadBase64);

            return System.Text.Encoding.UTF8.GetString(payloadBase64Bytes);
        }

        public JObject Uplink(JObject telemetryEvent, string payloadBase64, byte[] payloadBytes)
        {
            var payloadBase64Bytes = System.Convert.FromBase64String(payloadBase64);

            telemetryEvent.Add(""PayloadBase64"", payloadBase64Bytes);
            telemetryEvent.Add(""PayloadBytes"",System.Text.Encoding.UTF8.GetString(payloadBytes));

            return telemetryEvent;
        }

        public string Downlink(JObject command)
        {
            int temperature = command.Value<int>(""Temperature"");

            byte[] temperatureBytes = BitConverter.GetBytes(temperature);

            Array.Reverse(temperatureBytes);

            return System.Convert.ToBase64String(temperatureBytes);
        }
    }";
...
public void Execute6()
{
    string namespaces = $"using Newtonsoft.Json.Linq;using System;\n";
    string code1 = namespaces + codeSwarmSpaceFormatter1;
    string code2 = namespaces + codeSwarmSpaceFormatter2;

    JObject telemetry = new JObject
    {
        { "ApplicationID", 12345 },
        { "DeviceID", 54321 },
        { "DeviceType", 2 },
        { "ReceivedAtUtc", DateTime.UtcNow.ToString("s", CultureInfo.InvariantCulture) },
    };

    var formatters = new Dictionary<string, ISwarmSpaceFormatter>();

    Console.WriteLine($"Evaluator start");
    DateTime evaluatorStartAtUtc = DateTime.UtcNow;

    ISwarmSpaceFormatter SwarmSpaceFormatter1 = CSScript.Evaluator
                                  .LoadCode<ISwarmSpaceFormatter>(code1);

    ISwarmSpaceFormatter SwarmSpaceFormatter2 = CSScript.Evaluator
                                  .LoadCode<ISwarmSpaceFormatter>(code2);

    Console.WriteLine($"Evaluator:{DateTime.UtcNow - evaluatorStartAtUtc}");
    Console.WriteLine("");

    Console.WriteLine($"Evaluation start");
    DateTime evaluationStartUtc = DateTime.UtcNow;

    formatters.Add("F1", SwarmSpaceFormatter1);
    formatters.Add("F2", SwarmSpaceFormatter2);

    JObject command = new JObject
    {
        {"Temperature", 1},
    }; 

    ISwarmSpaceFormatter downlinkPayload;
    downlinkPayload = formatters["F1"];
    Console.WriteLine($"Downlink F1:{downlinkPayload.Downlink(command)}");
  
    downlinkPayload = formatters["F2"];
    Console.WriteLine($"Downlink F2:{downlinkPayload.Downlink(command)}");
  
    Console.WriteLine($"Evaluation:{DateTime.UtcNow - evaluationStartUtc}");
    Console.WriteLine("");

    const int iterations = 100;
    Console.WriteLine($"Evaluations start {iterations}");
    DateTime evaluationsStartUtc = DateTime.UtcNow;

    for (int i = 1; i <= iterations; i++)
    {
        JObject command1 = new JObject
        {
            {"Temperature", 1},
        };

        downlinkPayload = formatters["F1"];
        Console.WriteLine($" Downlink F1:{downlinkPayload.Downlink(command1)}");
       
        downlinkPayload = formatters["F2"];
        Console.WriteLine($" Downlink F2:{downlinkPayload.Downlink(command1)}");
    }

    Console.WriteLine($"Evaluations:{iterations} Took:{DateTime.UtcNow - evaluationsStartUtc}");
}

On my development box the initial “compile” of each function was taking approximately 2.1 seconds so I cached the “compiled” formatters in a dictionary so they could be reused. Cached in the dictionary executing the two formatters 100 times took approximately 15 milliseconds (which is close to native .NET performance).

Compatibility

To check that the CS-Script tooling could run on a machine without the .NET 6 Software Development Kit (SDK) I tested the application on a laptop which had a “fresh” install of Windows 10.

CS-Script application failing due to missing .NET 6 runtime
Installing the .NET 6 Runtime
CS-Script application running after .NET runtime installation

The CS-Script library is pretty amazing and has made the development of uplink and downlink payload formatters significantly less complex than I was expecting.

Swarm Space – FromDevice with webhooks

I modified my TTI V3 Connector Azure Storage Queues project which uses Azure Functions HTTP Triggers to put messages into Azure Storage Queues to process Swarm FromDevice Webhook messages.

First step was to configure a webhook with the Swarm dashboard

Swarm dashboard webhooks configuration

I configured the webhook, and to “acknowledge messages on successful delivery”. Then checked my configuration with a couple of “Test” messages.

Swarm dashboard webhook configuration

The Swagger API documentation has methods for configuring endpoints which can be called by an application.

Swagger API Documentation for managing endpoints

I queued a couple of messages on my Satellite Transceiver Breakout and when the next satellite passed overhead, shortly after they were visible in the Swarm Dashboard Messages tab.

Swarm Dashboard with test and live fromdevice messages

The messages were also delivered to an Azure Storage Queue, and I could view them with Azure Storage Explorer.

Azure Storage Explorer displaying a webhook message payload

Swarm Space – Azure IoT Basic Client

To figure out how to poll the Swarm Hive API I have built yet another “nasty” Proof of Concept (PoC) which gets ToDevice and FromDevice messages. Initially I have focused on polling as the volume of messages from my single device is pretty low (WebHooks will be covered in a future post).

Like my Azure IoT The Things Industry connector I use Alastair Crabtrees’s LazyCache to store Azured IoT Hub DeviceClient instances.

NOTE: Swarm Space technical support clarified the parameter values required to get FromDevice and ToDevice messages using the Bumbleebee Hive API.

Swarm API Docs messages functionality

The Messages Get method has a lot of parameters for filtering and paging the response message lists. Many of the parameters have default values so can be null or left blank.

Swarm API Get User Message filters

I started off by seeing if I could duplicate the functionality of the user interface and get a list of all ToDevice and FromDevice messages.

Swarm Dashboard messages list

I first called the Messages Get method with the direction set to “fromdevice” (Odd this is a string rather than an enumeration) and the messages I had sent from my Sparkfun Satellite Transceiver Breakout – Swarm M138 were displayed.

Swarm API Docs displaying “fromdevice” messages

I then called the Messages Get method with the direction set to “all” and only the FromDevice messages were displayed which I wasn’t expecting.

Swarm API Docs displaying ToDevice and FromDevices messages

I then called the Messages Get method with the direction set to “FromDevice and no messages were displayed which I wasn’t expecting

Swarm API Docs displaying “todevice” messages

I then called the Message Get method with the messageId of a ToDevice message and the detailed message information was displayed.

Swarm API Docs displaying the details of a specific inbound message

For testing I configured 5 devices (a real device and the others simulated) in my Azure IoT Hub with the Swarm Device ID ued as the Azure IoT Hub device ID.

Devices configured in Azure IoT Hub

My console application calls the Swarm Bumblebee Hive API Login method, then uses Azure IoT Hub DeviceClient SendEventAsync upload device telemetry.

Nasty console application processing the three “fromdevice” messages which have not been acknowledged.

The console application stores the Swarm Hive API username, password and the Azure IoT Hub Device Connection string locally using the UserSecretsConfigurationExtension.

internal class Program
{
    private static string AzureIoTHubConnectionString = "";
    private readonly static IAppCache _DeviceClients = new CachingService();

    static async Task Main(string[] args)
    {
        Debug.WriteLine("devMobile.SwarmSpace.Hive.AzureIoTHubBasicClient starting");

        IConfiguration configuration = new ConfigurationBuilder()
            .SetBasePath(Directory.GetCurrentDirectory())
            .AddJsonFile("appsettings.json")
            .AddUserSecrets("b4073481-67e9-41bd-bf98-7d2029a0b391").Build();

        AzureIoTHubConnectionString = configuration.GetConnectionString("AzureIoTHub");

        using (HttpClient httpClient = new HttpClient())
        {
            BumblebeeHiveClient.Client client = new BumblebeeHiveClient.Client(httpClient);

            client.BaseUrl = configuration.GetRequiredSection("SwarmConnection").GetRequiredSection("BaseURL").Value;

            BumblebeeHiveClient.LoginForm loginForm = new BumblebeeHiveClient.LoginForm();

            loginForm.Username = configuration.GetRequiredSection("SwarmConnection").GetRequiredSection("UserName").Value;
            loginForm.Password = configuration.GetRequiredSection("SwarmConnection").GetRequiredSection("Password").Value;

            BumblebeeHiveClient.Response response = await client.PostLoginAsync(loginForm);

            Debug.WriteLine($"Token :{response.Token[..5]}.....{response.Token[^5..]}");

            string apiKey = "bearer " + response.Token;
            httpClient.DefaultRequestHeaders.Add("Authorization", apiKey);

            var devices = await client.GetDevicesAsync(null, null, null, null, null, null, null, null, null);

            foreach (BumblebeeHiveClient.Device device in devices)
            {
                Debug.WriteLine($" Id:{device.DeviceId} Name:{device.DeviceName} Type:{device.DeviceType} Organisation:{device.OrganizationId}");

                DeviceClient deviceClient = await _DeviceClients.GetOrAddAsync<DeviceClient>(device.DeviceId.ToString(), (ICacheEntry x) => IoTHubConnectAsync(device.DeviceId.ToString()), memoryCacheEntryOptions);
            }

            foreach (BumblebeeHiveClient.Device device in devices)
            {
                DeviceClient deviceClient = await _DeviceClients.GetAsync<DeviceClient>(device.DeviceId.ToString());

                var messages = await client.GetMessagesAsync(null, null, null, device.DeviceId.ToString(), null, null, null, null, null, null, "all", null, null);
                foreach (var message in messages)
                {
                    Debug.WriteLine($" PacketId:{message.PacketId} Status:{message.Status} Direction:{message.Direction} Length:{message.Len} Data: {BitConverter.ToString(message.Data)}");

                    JObject telemetryEvent = new JObject
                    {
                        { "DeviceID", device.DeviceId },
                        { "ReceivedAtUtc", DateTime.UtcNow.ToString("s", CultureInfo.InvariantCulture) },
                    };

                    telemetryEvent.Add("Payload",BitConverter.ToString(message.Data));

                    using (Message telemetryMessage = new Message(Encoding.ASCII.GetBytes(JsonConvert.SerializeObject(telemetryEvent))))
                    {
                        telemetryMessage.Properties.Add("iothub-creation-time-utc", message.HiveRxTime.ToString("s", CultureInfo.InvariantCulture));

                        await deviceClient.SendEventAsync(telemetryMessage);
                    };

                    //BumblebeeHiveClient.PacketPostReturn packetPostReturn = await client.AckRxMessageAsync(message.PacketId, null);
                }
            }

            foreach (BumblebeeHiveClient.Device device in devices)
            {
                DeviceClient deviceClient = await _DeviceClients.GetAsync<DeviceClient>(device.DeviceId.ToString());

                await deviceClient.CloseAsync();
            }
        }
    }

    private static async Task<DeviceClient> IoTHubConnectAsync(string deviceId)
    {
        DeviceClient deviceClient;

        deviceClient = DeviceClient.CreateFromConnectionString(AzureIoTHubConnectionString, deviceId, TransportSettings);

        await deviceClient.OpenAsync();

        return deviceClient;
    }

    private static readonly MemoryCacheEntryOptions memoryCacheEntryOptions = new MemoryCacheEntryOptions()
    {
        Priority = CacheItemPriority.NeverRemove
    };

    private static readonly ITransportSettings[] TransportSettings = new ITransportSettings[]
    {
        new AmqpTransportSettings(TransportType.Amqp_Tcp_Only)
        {
            AmqpConnectionPoolSettings = new AmqpConnectionPoolSettings()
            {
                Pooling = true,
            }
        }
    };
}

While testing I disabled the message RxAck functionality so I could repeatedly call the MessagesGet method so I didn’t have to send new messages and burn through my 50 free messages.

Azure IoT Explorer telemetry displaying the three messages processed by my console application.

.

Updated parameters based on feedback from Swarm technical support

Need to have status set to -1