Is TCP Guaranteed to arrive in order?

python tcp twisted protocols
Smashery picture Smashery · Nov 7, 2009 · Viewed 25.2k times · Source

If I send two TCP messages, do I need to handle the case where the latter arrives before the former? Or is it guaranteed to arrive in the order I send it? I assume that this is not a Twisted-specific example, because it should conform to the TCP standard, but if anyone familiar with Twisted could provide a Twisted-specific answer for my own peace of mind, that'd be appreciated :-)

Answer

Jeffrey Hantin picture Jeffrey Hantin · Nov 7, 2009

As long as the two messages were sent on the same TCP connection, order will be maintained. If multiple connections are opened between the same pair of processes, you may be in trouble.

Regarding Twisted, or any other asynchronous event system: I expect you'll get the dataReceived messages in the order that bytes are received. However, if you start pushing work off onto deferred calls, you can, erm... "twist" your control flow beyond recognition.

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