Unable to abort a FTP command?

billiejoex gnewsg at gmail.com
Wed Jul 25 14:32:02 CEST 2007


On 25 Lug, 09:48, _... at 163.com wrote:
> Hi,
>     I write the following script to retrieve a part of a large file
> from a FTP site:
>
> import ftplib
>
> class ftp_getter(object):
>
>     def __init__(self):
>         self.handle = ftplib.FTP('ftp_server_address')
>         self.handle.set_debuglevel(2)
>         self.login()
>
>     def login(self):
>         self.handle.login('user', 'pass')
>         self.handle.cwd('/temp1/')
>
>     def quit(self, is_close = False):
>         self.handle.quit()
>         if is_close:
>             self.handle.close()
>             print 'ftp handle closed'
>
>     def getpart_callback(self, received):
>         print "received a packet"
>         if self.cnt <= 0:
>             if not self.outf.closed:
>                 self.outf.close()
>             if not self.aborted:
>                 try:
>                     self.handle.abort()
>                     self.aborted = True
>                 except Exception,ex:
>                     pass
>         else:
>             print 'received packet, [0] = %x' % ord(received[0])
>             self.outf.write(received)
>             self.cnt -= len(received)
>
>     def getpart(self, ftp_filename, rest, cnt, out_filename):
>         self.outf = open(out_filename, 'wb')
>         self.cnt = cnt
>         self.aborted = False
>         self.handle.retrbinary('RETR ' + ftp_filename,
> self.getpart_callback, 8192, rest)
>         if not self.outf.closed:
>             self.outf.close()
>
> if __name__ == '__main__':
>     g = ftp_getter()
>     g.getpart('FILE_TO_RETRIEVE.DAT', 50000, 20, 'out.dat')
>     g.quit(True)
>     print "all done."
>
>     As the last four lines shown, I want to connect to my FTP server,
> retrieve 20 bytes starting at offset 50000 from FILE_TO_RETRIEVE.DAT,
> and stop retrieving after more than 20 bytes have been received. It's
> quite simple, but to my suprise, this code does not work.
> "self.handle.abort()" have been executed and I got the expected
> response from server(426),  but the RETR command does not seem to stop
> at all. More and more data are received and getpart_callback method is
> called again and again.
>     Why the RETR command is not actually aborted? Can anyone help me?
>
>     Thanks
>
>     Xu Wang

I would *strongly* rencommend avoid using ABOR.
The easiest way to abort the data transfer is to simply close the data
connection.
Instead of using ftp.retrbinary you could 'handle' the data connetion
('manually') by yourself.
The code below starts RETRieving a file, and quit when more than 2^19
bytes are transmitted (not tested).
Hope this helps.


fd = open('retrieved_file', 'wb')

ftp = ftplib.FTP()
ftp.connect(host=host, port=port)
ftp.login(user=user, passwd=pwd)

# use binary transfer type
ftp.voidcmd('TYPE I')
conn = ftp.transfercmd('retr 1.tmp', rest=None)
bytes_recv = 0
while 1:
    chunk = conn.recv(8192)
    # stop transfer while it isn't finished yet
    if bytes_recv >= 524288: # 2^19
        break
    elif not chunk:
        break
    fd.write(chunk)
    bytes_recv += len(chunk)
conn.close()
# here we should get a 426 response
ftp.voidresp()
fd.close()
ftp.close()




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