问题:

I know that UDP is inherently unreliable, but when connecting to localhost I would expect the kernel handles the connection differently since everything can be handled internally. So in this special case, is UDP considered a reliable protocol, or will the kernel still potentially junk some packets if buffers are overrun?

回答1:

I repeat a previous answer to a related question. To remain portable always anticipate your UDP sockets might drop packets or receive out of order data.

回答2:

I have seen UDP to localhost dropping packets. We think we were overloading the kernel queue. All we know for sure is that it was dropping packets.

回答3:

I don't think that UDP (or any other network protocol) says anything about different behavior when connecting to localhost. So the answer will depend on the specific kernel that you're using. Best to assume that UDP will behave like UDP.