mport ftplib, sys  ftp1 = ftplib.FTP('127.0.0.1', 'book', 'bookpw')  ftp1.cwd('/Dir')  ftp2 = ftplib.FTP('www.xxxx.com', 'xxx', 'xxxps')  ftp2.cwd('/public')  sock1 = ftp1.transfercmd('RETR a.zip')  sock2 = ftp2.transfercmd('STOR b.zip')    flen = 0                              while 1:      block = sock1.recv(1024)              if len(block) == 0:                       break      flen += len(block)                    while len(block) > 0:                     sentlen = sock2.send(block)           block = block[sentlen:]         print 'Transferred', flen, 'bytes'    sock1.close()  sock2.close()  ftp1.quit()  ftp2.quit()