On 10/06/2011 05:22 PM, Fabian Rothfuchs wrote:
> I also ran a tcpdump to confirm – The opposite server is obviously
> pushing content to the socket in arbitrary frequencies, ending up in my
> dataReceived() method to get called arbitrarily as well.
Yes, this is normal. TCP stacks are free to segment the data as they see
fit. Machine-readable protocols have framing for this reason. Sadly,
text streams run over telnet/SSH/CLI interfaces are usually badly
framed, if at all.
>
> My question: is there any best practice for buffer techniques here?
Twisted comes with a bunch of higher level protocol sub-classes that
buffer the data for you, then deliver chunks of the buffer to methods on
your class.
For example, lineReceiver delivers whole lines.
There may well be a conch helper class that does the same.
The generic do-it-yourself approach is to append the data to a buffer,
then look for complete protocol messages in the buffer and process them
in order, possibly with a state machine. e.g.
def dataReceived(self, data):
self.buffer += data
if self.state=='waiting-for-userid':
if 'USERID:' in self.buffer:
# send userid
self.transport.write('0004\r')
self.state = 'waiting-for-password'
# empty the buffer
self.buffer = ''
elif self.state=='waiting-for-password':
if 'PASSWORD:' in self.buffer:
self.transport.write(password+'\r')
self.state = 'logged-in'
self.buffer = ''
...and so on. This is boring to write by hand, so see if there is
something in Twisted you can use already.
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