Why do we need EPOLLRDHUP when EPOLLHUP seems enough?

问题

According to the linux man page,

EPOLLHUP

When reading from a channel such as a pipe or a stream socket, this event merely indicates that the peer closed its end of the channel.

EPOLLRDHUP

Stream socket peer closed connection, or shut down writing half of connection.

I can hardly tell any difference between EPOLLHUP and EPOLLRDHUP.

To me, whenever EPOLLRDHUP is used EPOLLHUP can be used instead with the same semantics.

Am I right? If not, any explanations?

来源：https://stackoverflow.com/questions/51833215/why-do-we-need-epollrdhup-when-epollhup-seems-enough