unable to connect (wodSFTP / wodSFTP.NET / wodSFTPdll)

Hi,
I am using WeOnlyDo.Client trial version to connect to a remote server but I have problems.
I am using a library project which uses WeOnlyDo.Client library. When I try to connect there is no error but I think that it doesn't connect bacause when I try to put or get files I get the next error Invalid state. Connect first. Does anyone help me?
this is the code.

using System;
using System.Diagnostics;
using WeOnlyDo.Client;

namespace RepsolYPF.CCSi.TravelClub.CompClaseSFTP
{

[Serializable]
public class ClaseSFTP
{
SFTP sftp1 = new SFTP();

public int Ejecutar (string Tipo, string User, string Pwd, string Server, int Puerto, string PathYFileName, string chdir)
{
try
{
Conectar (Server,Puerto,User,Pwd);

if (Tipo == put )
SubirFichero(chdir,PathYFileName);
else if (Tipo == get )
ObtenerFichero(chdir,PathYFileName);
else
{
Desconectar();
return -1;
}
Console.WriteLine ( Ejecución con exito );
return 0;
}
catch (Exception ex)
{
Console.WriteLine ( No se ha podido ejecutar la operación indicada );
return -1;
}
}

private void Conectar(string Server, int Puerto, string User, string Pwd)
{
try
{
sftp1.Hostname = Server;
sftp1.Login = User;
sftp1.Password = Pwd;
sftp1.Port = Puerto;
sftp1.Connect();
Console.WriteLine( Ha conectado );
}
catch (Exception ex)
{
Console.WriteLine( Error al conectar. +ex.Message);
throw ex;
}
}

private void Desconectar ()
{
try
{
sftp1.Disconnect();
Console.WriteLine( Ha desconectado );
}
catch (Exception ex)
{
Console.WriteLine( Error al desconectar +ex.Message);
throw ex;
}
}

private void ObtenerFichero (string chdir, string PathYFileName)
{
try
{
Error = null;
sftp1.GetFile (chdir,PathYFileName);
Console.WriteLine ( Fichero descargado );
}
catch (Exception ex)
{
Console.WriteLine ( Error al descargar el fichero +ex.Message);
throw ex;
}
}

private void SubirFichero (string chdir, string PathYFileName)
{
try
{
sftp1.PutFile(PathYFileName,chdir);
Console.WriteLine ( Fichero subido );
}
catch (Exception ex)
{
Console.WriteLine ( Error al subir el fichero +ex.Message);
throw ex;
}
}
}
}