Short snippet to demo GAE sockets

import ftplib
import logging

ftp = ftplib.FTP('hostUrl', timeout=3600)
ftp.login('MyUsername', 'SecretPassword')
ftp.set_debuglevel(4)
filename = None
for entry in ftp.nlst():
    match = re.match(r'Customer_\d{5,6}\.txt', entry)
    if match:
        filename = match.string
src_file = cStringIO.StringIO()

def _callback_gen():
    total_len = [0]

    def callback(data):
        total_len[0] += len(data)
        src_file.write(data)
        if ((time.time() - starttime[0]) * 1000) > 6e4:
            logging.info('Bytes read: %i/%i' % (len(data), total_len[0])
            ftp.sendcmd('NOOP')
    return callback

ftp.retrbinary('RETR %s' % filename, callback_gen(), blocksize=131072)

ftp.quit()