Problem connecting Delphi client application to service via TCP/IP

I'm trying to connect my client application written in Delphi to a service running on a server using TCP/IP. The service is also written in Delphi and uses TIdTCPServer to listen for connections. When the client application tries to connect to the service, I get the error "Connection refused". The service seems to work fine and all listening and further steps (connecting to the database via ADO) take place in the thread.

Here's what I've already checked:

• The client application is using the correct IP address and port number to connect.

class function OperationThread.DefaultHost: string;
begin
  Result := '127.0.0.1';
end;
class function OperationThread.DefaultPort: Integer;
begin
  Result := 5000;
end;

• I've made sure that both the client and the server are using the same protocol (TCP). Server code (service):

procedure ServiceController(CtrlCode: DWord); stdcall;
begin
  MyService.Controller(CtrlCode);
end;

function TTestService2.GetServiceController: TServiceController;
begin
  Result := ServiceController;
end;

procedure TTestService2.ServiceExecute(Sender: TService);
begin
  while not Terminated do
  begin
    ServiceThread.ProcessRequests(False);
    TThread.Sleep(1000);
  end;
end;

procedure TTestService2.ServiceStart(Sender: TService; var Started: Boolean);
begin
  try
    FBackgroundThread := TBackgroundThread.Create(
      ADOConnection1, DBemployesConnection, ADOQuery1, ADOQuery2, ADOQuery3, IdTCPServer1);
    FBackgroundThread.Start;
    Started := True;
  except
    on E: Exception do
    begin
      Started := False;
    end;
  end;
end;

procedure TTestService2.ServiceStop(Sender: TService; var Stopped: Boolean);
begin
  try
    if Assigned(FBackgroundThread) then
    begin
      FBackgroundThread.Terminate;
      FBackgroundThread.WaitFor;
      FreeAndNil(FBackgroundThread);
    end;

    Stopped := True;
  except
    on E: Exception do
    begin
      Stopped := False;
    end;
  end;
end;

procedure TTestService2.ServicePause(Sender: TService; var Paused: Boolean);
begin
  FBackgroundThread.Pause;
  Paused := True;
end;

procedure TTestService2.ServiceContinue(Sender: TService; var Continued: Boolean);
begin
  FBackgroundThread.Continue;
  Continued := True;
end;

And thread code I use in my service:

constructor TBackgroundThread.Create(ADOConnection, DBEmployesConnection: TADOConnection;
  ADOQuery1, ADOQuery2, ADOQuery3: TADOQuery; IdTCPServer: TIdTCPServer);
begin
  inherited Create(True);
  FADOConnection := ADOConnection;
  FDBEmployesConnection := DBEmployesConnection;
  FADOQuery1 := ADOQuery1;
  FADOQuery2 := ADOQuery2;
  FADOQuery3 := ADOQuery3;
  FIdTCPServer := IdTCPServer;
  FreeOnTerminate := True;

  FADOConnection.Connected := True;
  FDBEmployesConnection.Connected := True;
  FIdTCPServer.Active := True;
end;
destructor TBackgroundThread.Destroy;
begin
  if Assigned(FADOConnection) then
    FADOConnection.Free;
  if Assigned(FDBEmployesConnection) then
    FDBEmployesConnection.Free;
  if Assigned(FADOQuery1) then
    FADOQuery1.Free;
  if Assigned(FADOQuery2) then
    FADOQuery2.Free;
  if Assigned(FADOQuery3) then
    FADOQuery3.Free;
    FIdTCPServer.Active := False;
  inherited;
end;

procedure TBackgroundThread.Continue;
begin
  FPaused := False;
end;

procedure TBackgroundThread.Execute;
begin
  CoInitialize(nil);
  try
  FIdTCPServer.OnExecute := IdTCPServer1Execute;
    while not Terminated do
    begin
      if not FPaused then
      begin
        // Główne zadania wątku
        // Na przykład przetwarzanie zapytań, jeśli istnieją
      end
      else
      begin
        Sleep(100);
      end;

      Sleep(10);
    end;
    FIdTCPServer.Active := False;
  finally
    CoUninitialize;
  end;
end;

procedure TBackgroundThread.IdTCPServer1Execute(AContext: TIdContext);
var
  Request: string;
  Response: string;
begin
  try
    Request := AContext.Connection.IOHandler.ReadLn;
    ProcessRequest(Request, Response);
    AContext.Connection.IOHandler.WriteLn(Response);
  except
    on E: Exception do
    begin
      Response := '{"status":"error", "message":"Błąd podczas przetwarzania zadania: ' + E.Message + '"}';
      AContext.Connection.IOHandler.WriteLn(Response);
    end;
  end;
end;

procedure TBackgroundThread.Pause;
begin
  FPaused := True;
end;

Rest of the code id not important and works well.