title: jsch channel is not opened
body: <p>i'm trying to open an exec and an sftp channel simultaneously but when i open the sftp channel gives me an error, the code (simplified) is this:</p>
  
  <pre><code>JSch connection = new JSch();
  Session session = connection.getSession(user, ip, port);
  session.setPassword(password);
  session.connect(15000);
  ChannelExec channel = (ChannelExec) session.openChannel("exec");
  //exec commands whit channel
  Channel ch;
  ch = ssh.session.openChannel("sftp");
  ch.connect();//-------ERROR!
  ChannelSftp sftp = (ChannelSftp)ch;
  </code></pre>
  
  <p>the error is: "com.jcraft.jsch.JSchException: channel is not opened."</p>