> Proper behavior for ftplib when sending is to send all desired data, 
> then call "sock.shutdown(socket.SHUT_RDWR)".  This indicates that no 
> more data will be sent, and blocks until the receiver has acknowledged 
> all their data. 

I'm not sure about this. Such a requirement should be respected by both peers and AFAICR there's no FTP-related RFC which explicitly states that shutdown() should be used.

http://www.rfc-archive.org/getrfc.php?rfc=4217 chapter 12.4 should reflect the same use case we're talking about: a client sending a file (STOR).
In the example only close() is used, which perhaps should lead this discussion to question whether socket's close() method is implemented properly, as your linux man quote suggests.