c# - Open data stream (FTP AUTH TLS)

Question

I communicate with a FTP server that requires AUTH TLS.
So I created a NetworkStream and sent AUTH TLS. After this I created a SslStream with the NetworkStream as InnerStream and sent USER user and PASS pass.

After this, I can use PWD, etc., but when I want to download a file with RETR, the server want a new channel.

How can I open this channel to receive the file data?