Accessing DataSocket Server with Python

[Marko Rauhamaa]

Chris Angelico <rosuav at gmail.com>:

> Indeed. That said, though, if your writes are all smaller than one
> packet, and you perfectly alternate a write and a read, a write and a
> read, at both ends, then you can go a very long way without ever
> running into this.

Rare errors are worse than consistent errors.

TCP streams are intercepted by address translators, load balancers,
proxies, protocol translators and what not. They will eagerly take
advantage of the fact that TCP is a full-duplex octet stream.

Also, programs could be plugged into other types of octet stream with
other stream chopping characteristics.

Finally, the MTU size is very unpredictable. You have all kinds of
encapsulation (6to4, VPN, VLAN, tunneling etc) that make it difficult to
be sure about what's a "small" write.

What's more, you should be on the lookout for partial writes not block
until they finish. Typically, it is not enough to rely on TCP's flow
control but also impose a separate application-level, end-to-end flow
control to avoid deadlocks on the one hand and buffer overflows on the
other hand.


Marko