Main FTPHost session times out while downloading a large file

[schwa]

If an upload or download is started whose duration exceeds the timeout setting of the server, the main FTP session which spawned the child session will time out even though the upload/download will succeed. That is, any direct access (that works on the server) to the original FTPHost object will result in a traceback.

(problem  reported by Henning Hraban Ramm)

[schwa]

The traceback gotten by Henning is

Traceback (most recent call last):
  File "./ftpsync.py", line 388, in <module>
    host.rename(sourcepath, host.path.join(root, abgeholtdir, f))
  File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/ftputil-2.4.2-py2.6.egg/ftputil/ftputil.py", line 746, in rename
    self._check_inaccessible_login_directory()
  File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/ftputil-2.4.2-py2.6.egg/ftputil/ftputil.py", line 535, in _check_inaccessible_login_directory
    self.chdir(presumable_login_dir)
  File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/ftputil-2.4.2-py2.6.egg/ftputil/ftputil.py", line 587, in chdir
    ftp_error._try_with_oserror(self._session.cwd, path)
  File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/ftputil-2.4.2-py2.6.egg/ftputil/ftp_error.py", line 146, in _try_with_oserror
    raise TemporaryError(*exc.args)
ftputil.ftp_error.TemporaryError: 421 No Transfer Timeout (300 seconds): closing control connection.
Debugging info: ftputil 2.4.2, Python 2.6.4 (darwin)

and he adds:

The mentioned line (host.rename) is right after: host.download_if_newer(sourcepath, targetpath, mode='b') with host being a ftputil.FTPHost

[schwa]

In my opinion, this isn't a defect in ftputil because FTP servers are free to let connections time out.

I agree, though, that ftputil's behavior may seem confusing. Some background is  provided here.

[schwa]

To make it easier to keep the connection alive, I've added a keep_alive method in revision [ac645c973d1b]. Note that this only works on the "main" connection of the FTPHost instance. It will not help if a child session times out during a file transfer.