Linux, C, epoll(), read() data incompleted?

Question

Linux, C. Below issue only happens by using epoll(). If I use select() on server socket, there is no data loss.

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Update: I received

Answer 1

        break;  //I do received 2 errors of Try Again. How to try again?

By going back to your epoll loop.

        data: 60734  //??? why I am not able to read all 65536 bytes?

Because they hadn't been received yet.

I think you may miss the big picture on how you do non-blocking I/O with epoll.

1. epoll tells you when there's data.
2. You read as much as you can at that time.
3. You go back to step 1.