I’m using epoll as level triggered. According to recv(3), if recv returns 0 “no messages are available to be received and the peer has performed an orderly shutdown”. Does this mean that the whole request has been received and the socket has been closed on the other side? That the socket has been closed on both ends? Or that simply the whole request has been received and the socket is awaiting a response to be written to it? Any help would be greatly appreciated.
According to What value will recv() return, it sounds like if recv returns 0, the connection is closed on the other side. If this is the case, what needs to be done on the epoll side? Does the socket need to be completely removed with a call to epoll_ctl with EPOLL_CTL_DEL and a call to close?
It means that you have already read all the data that has been sent overthe connection, and the only thing left is a TCP FIN, which could be the result of either a full close by the remote or a shutdown for output by the remote. You can’t do much but close the socket at this point, unless you know the peer has only shutdown, in which case you can still write to the socket. Your application protocol determines all that.
There is no such thing as a request or response in TCP. There is just a bidirectional byte-stream.