Thanks for that explanation David. Makes sense! On Wed, 2010-02-10 at 16:01 -0500, David Bolen wrote:
> Darren Govoni <dar...@ontrenet.com> writes: > > >>From what I learned in other posts, the dataReceived(self, data): in the > > Echo server > > will get called with out-of-order data/bytes from the client. Of course, > > I could be misinformed, > > but what I understood before was that in this type of Protocol, I would > > have to re-order > > and re-assemble the bytes. And I'm trying to avoid that, since of > > course, TCP already does it. > > Data being received out of order can't happen, as long as the Protocol > is layered on top of TCP, since as you say, TCP already provides that > guarantee. The dataReceived() method is really just how the data > being received from TCP is handed to the Protocol object. > > UDP can be out of order, as it provides very few guarantees above and > beyond IP itself. But I'm not sure you can layer an IProtocol over > UDP with Twisted. > > There is a general issue where you may receive the data in differently > sized chunks in dataReceived() than it might have been transmitted > originally, which is a common source of confusion to people new to > stream protocols, so perhaps you were thinking of that issue? > > The stream nature (and possibility for early disconnect from the > client) is why having some internal length information for bulk > transfers is sensible. For your original question, I was going to > suggest an older posting of mine for a similar situation where I needed > a bulk upload to augment a PB-based server, but it appears that you've > located it in the archives yourself. > > > But like I said, I could have been misinformed because it seems pretty > > basic to write 1,2,3 > > to a server and have it received 1,2,3, guaranteed. > > Yes - TCP guarantees that what you transmit at one end will be > received in order at the other end or not at all (e.g., outages, > disconnects, etc...). It has a weaker guarantee in terms of no > corruption, but one that is, in combination with typical link layer > protections, generally more than sufficient for the vast majority of > connections using it each day. > > -- David > > > _______________________________________________ > Twisted-Python mailing list > Twisted-Python@twistedmatrix.com > http://twistedmatrix.com/cgi-bin/mailman/listinfo/twisted-python
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