One of the major differences between old and new .NET Core SignalR is that automatic reconnects are not supported. This means that you need explicitly open a new connection if you lost connection to the server.

I managed to write my own implementation that do automatic reconnects on this new version of .NET Core 2 SignalR that works for me.

The code bellow uses Polly for automatic retry policy and Serilog for logging.

Here is my implementation. Hope someone will find it useful:

var signalRConnection = new HubConnectionBuilder()
     .WithUrl(BaseUrl + "/hubs/integrationserver", options =>
     {
      options.Headers.Add("Authorization", "Basic " + Header);
     }).Build();
signalRConnection.On<string, string>("ReceiveMessage", (entityName, json) =>
{

       
});

private async void OpenSignalRConnection()
{

     var pauseBetweenFailures = TimeSpan.FromSeconds(20);
     var retryPolicy = Policy
         .Handle<Exception>()
         .WaitAndRetryForeverAsync(i => pauseBetweenFailures
         , (exception, timeSpan) => {
             Log.Error(exception.ToString());
         });

     await retryPolicy.ExecuteAsync(async () =>
     {
         Log.Information("Trying to connect to SignalR server");
         await TryOpenSignalRConnection();
     });
}

private async Task<bool> TryOpenSignalRConnection()
{
     Log.Information("Starting SignalR connection");
     await signalRConnection.StartAsync();

     Log.Information("SignalR connection established");

     return true;

}

private async Task SignalRConnection_Closed(Exception arg)
{

     Log.Information("SignalR connection is closed");
     await signalRConnection.StopAsync();
     signalRConnection.Closed -= SignalRConnection_Closed;

     OpenSignalRConnection();

}