I have a FTP connection from which I am downloading many files and processing them in between. I'd like to be able to check that my FTP connection hasn't timed out in between. So the code looks something like:
conn = FTP(host='blah')
conn.connect()
for item in list_of_items:
myfile = open('filename', 'w')
conn.retrbinary('stuff", myfile)
### do some parsing ###
How can I check my FTP connection in case it timed out during the ### do some parsing ### line?
Send a NOOP command. This does nothing but check that the connection is still going and if you do it periodically it can keep the connection alive.
For example:
conn.voidcmd("NOOP")
If there is a problem with the connection then the FTP object will throw an exception. You can see from the documentation that exceptions are thrown if there is an error:
socket.error and IOError: These are raised by the socket connection and are most likely the ones you are interested in.
exception ftplib.error_reply: Exception raised when an unexpected reply is received from the server.
exception ftplib.error_temp: Exception raised when an error code signifying a temporary error (response codes in the range 400–499) is received.
exception ftplib.error_perm: Exception raised when an error code signifying a permanent error (response codes in the range 500–599) is received.
exception ftplib.error_proto: Exception raised when a reply is received from the server that does not fit the response specifications of the File Transfer Protocol, i.e. begin with a digit in the range 1–5.
Therefore you can use a try-catch block to detect the error and handle it accordingly.
For example this sample of code will catch an IOError, tell you about it and then retry the operation:
retry = True
while (retry):
try:
conn = FTP('blah')
conn.connect()
for item in list_of_items:
myfile = open('filename', 'w')
conn.retrbinary('stuff', myfile)
### do some parsing ###
retry = False
except IOError as e:
print "I/O error({0}): {1}".format(e.errno, e.strerror)
print "Retrying..."
retry = True
