The SelectCommand.Connection property has not been initialized. MySql

It turns out that I'm working with SignalR, where in the html view I make the following request to the client:

 var myHub = $.connection.myHub;
        var direccionWeb = $("#direccionWeb").val().toString();
        $.connection.hub.url = direccionWeb + "/signalr";
        $.connection.hub.start().done(function () {
            myHub.server.broadcastMessageToPrinterReportTicket(global_venta, global_mesa, nombregarzon, idgrupo, grupo);

        }).fail(function (error) {
            console.error(error);
        });

In the Hub file I have the following:

public void BroadcastMessageToPrinterReportTicket(String global_venta,String global_mesa,String nombregarzon,String idgrupo, String grupo)
    {
        string nombreImpresora = grupo;
        DataTable dt = new DataTable();

        string sql = "SELECT " +
            "cantidad," +
            "detalle " +
            "FROM producto " +                
            "WHERE venta=@global_venta AND venta>0 AND menu.grupo=@idgrupo AND comandasd.pedido=0";
        conexion.conectar(); 

        using (MySqlCommand command = new MySqlCommand(sql, conexion.con))
        {
            command.Parameters.AddWithValue("@global_venta", global_venta);
            command.Parameters.AddWithValue("@idgrupo", idgrupo);
            using (MySqlDataAdapter reader = new MySqlDataAdapter(command))
            {
                using (MySqlDataAdapter sda = new MySqlDataAdapter(command))
                {
                    sda.Fill(dt);
                }
            }
        }
        conexion.cerrar();


        Clients.All.imprimeReport(datos, ........);
    }

The file that contains the connection class is the following:

public void conectar()
    {
        try
        {
            string ip = HttpContext.Current.Session["ip"].ToString();
            string db = HttpContext.Current.Session["db"].ToString();
            string user = HttpContext.Current.Session["user"].ToString();
            string pass = HttpContext.Current.Session["pass"].ToString();

            con = new MySqlConnection("server=" + ip + ";user id=" + user + ";password=" + pass + ";database=" + db + ";port=3306;Allow User Variables=true"); 
            con.Open();
        }
        catch
        {

        }
    }

But when I try to add data to the DataTable, that is to say on the line where it says sda.Fill (dt), I get the following error: The SelectCommand.Connection property has not been initialized.

The strange thing that when I use is the same function declared in the controller, it works correctly. What I want is to be able to obtain a datatable with the parameters that BroadcastMessageToPrinterReportTicket receives and send it to the client.

If someone knew how to correct the error, or some help, it would be appreciated.

Greetings