No connection could be made because the target machine actively refused it 127.0.0.1:5566

I have a problem with my selenium test, when I try to run nothing happens and after 5 seconds it stopped, when i try to debug it, there appears error: enter image description here

And this is full error message:

OpenQA.Selenium.WebDriverException: 'Unexpected error. System.Net.WebException: Unable to connect to the remote server ---> System.Net.Sockets.SocketException: No connection could be made because the target machine actively refused it 127.0.0.1:5566
   at System.Net.Sockets.Socket.DoConnect(EndPoint endPointSnapshot, SocketAddress socketAddress)
   at System.Net.ServicePoint.ConnectSocketInternal(Boolean connectFailure, Socket s4, Socket s6, Socket& socket, IPAddress& address, ConnectSocketState state, IAsyncResult asyncResult, Exception& exception)
   --- End of inner exception stack trace ---
   at System.Net.HttpWebRequest.GetRequestStream(TransportContext& context)
   at System.Net.HttpWebRequest.GetRequestStream()
   at OpenQA.Selenium.Remote.HttpCommandExecutor.Execute(Command commandToExecute)
   at OpenQA.Selenium.Remote.RemoteWebDriver.Execute(String driverCommandToExecute, Dictionary`2 parameters)'

What does it means "no connection because machine actively refused it 127.0.0.1:5566", how it is possible to change this connection, if it is necessary and how I can find right connection?

A piece of code where it is an error:

namespace DVSTesti.Common
{
    public class CustomRemoteWebDriver : RemoteWebDriver
    {
        public static bool useExistingSession = false;

        public static string sessiodIdPath = String.Format(@"{0}\..\..\sessionID.txt", AppDomain.CurrentDomain.BaseDirectory);

        public CustomRemoteWebDriver(Uri remoteAddress, DesiredCapabilities dd)
            : base(remoteAddress, dd)
        {
        }

        protected override Response Execute(string driverCommandToExecute, System.Collections.Generic.Dictionary<string,object> parameters)

        {
            if (driverCommandToExecute == DriverCommand.NewSession)
                return ProcessNewSessionAction(parameters);
            else
                return base.Execute(driverCommandToExecute, parameters);
        }

        private Response ProcessNewSessionAction(Dictionary<string, object> parameters)
        {
            useExistingSession = false;

            if (useExistingSession)
            {

                var sidText = File.ReadAllText(sessiodIdPath);
                return new Response
                {
                    SessionId = sidText,
                };
            }
            else
            {
                var response = base.Execute(DriverCommand.NewSession, parameters);
                File.WriteAllText(sessiodIdPath, response.SessionId);
                return response;
            }

        }
    }
}