SignalR on Azure sends message to SignalR client within a LAN - windows-services

Question

We have the following mixed-environment scenario (Azure and LAN):
Azure Web App calls a method in the Azure API (triggered by some user action in the web app).
This Azure API then establishes a SignalR HubContext connection .
The HubContext broadcasts a message.
The SignalR client (consuming the message) is a Windows Service installed on a machine on the LAN, behind the firewall.
Our client is complaining that the connection often breaks, and therefore several messages are missing on a daily basis.
Here is a test method in the Azure API, which attempts to broadcast a message:
using Microsoft.AspNet.SignalR;
using System;
using System.IO;
using System.Net.Http.Headers;
using System.Reflection;
using System.Runtime.Caching;
using System.Text;
using System.Web.Http;
using System.Xml;
...
namespace MyTestAPI.Controllers
[AllowCrossSiteJson]
[RoutePrefix("api/Test")]
public class HL7Controller : ApiController
[HttpGet]
[Route("TestSignalR")]
public IHttpActionResult TestSignalR()
{
string reportData = $"<TestReport>This is a test message generated on { DateTime.Now }.</TestReport>";
var hubContext = GlobalHost.ConnectionManager.GetHubContext<HL7Hub>();
hubContext.Clients.All.SendReportData(reportData);
return Ok(reportData);
}
...
}
And in the client's environment, there's a Win Service installed - it acts as the SignalR Client
And here's a snippet of our H..NotificationsService solution (vs2019, Framework 4.6.1)
using log4net.Ext.EventID;
using Microsoft.AspNet.SignalR.Client;
using System;
using System.Configuration;
using System.Diagnostics;
using System.Net;
using System.ServiceProcess;
using System.Threading;
namespace H_NotificationSrv
{
public partial class H_NotificationService : ServiceBase
public async void StartListner()
{
try
{
var hubConnection = new HubConnection(hl7APIUrl);
hubConnection.Credentials = CredentialCache.DefaultNetworkCredentials;
var hubProxy = hubConnection.CreateHubProxy("MyTestHub");
hubProxy.On<string>("SendReportData", reportData =>
{
SendReportDataToSomeone(reportData);
});
await hubConnection.Start();
}
catch (Exception ex)
{
string errorMessage = ex.Message;
if (ex.InnerException != null)
errorMessage += " Inner Exception: " + ex.InnerException.Message;
applog.Error(errorMessage);
}
}
}
}