如何防止对TCP套接字的延迟回复？

Question

I'm writing a database library that will have to intelligently support timeouts. Now that I'm looking at connection pooling, I'm particularly worried about the following scenario:

1. Send Query #1
2. Time out after n seconds.
3. Send Query #2
4. Receive a response to query #1

Step four can happen, because the queries are not marked with a query ID: all I know is I've received a response, and I don't know which query it belongs to. One could argue that this constitutes a mistake in the protocol, but that's not up to me.

Before sending query #2, what should I do to the socket to avoid such a late reply? Is the only correct way to shutdown() , close() and re- connect() ?

Answer 1

I am afraid this is the only safe way to operate your connection, because there is no other way to get a one-to-one between question and answer over TCP. There seems to be a lack of some sort of a cancel function inbetween.

This reference gives more insight: http://www.ssfnet.org/Exchange/tcp/tcpTutorialNotes.html