Disconnect a socket If Foundry meets EOF while reading the socket

[majecty]

This PR fixes #308

There are a few things to do more.

1. Should we catch the error in the places?
2. What should we do when we met other IO errors? Should we disconnect the socket?
3. What happens if we write bytes to a disconnected socket? (This PR only checks the read call).

[sgkim126]

@majecty

1. I think it's fine.

2. We should not close the connection if the error is WouldBlock or Interrupted.
   I'm not sure whether WriteZero will occur in the non-blocking socket.
   In my opinion, InvalidInput, InvalidOutput or TimeOut will not occur in our code.
   We'd better handle ConnectionReset and BrokenPipe, but I'm not sure there is a hup event or not in these cases.
   I think other errors will not occur while sending/receiving data.

3. It's good if we can detect an error, but I suspect that the underlying implementation returns WouldBlock because we use a non-blocking socket. If it does, we cannot detect whether the connection has closed or there is just congestion.

[majecty]

@sgkim126 Thanks I'll develop this PR.

I found these sentences from the Write document.

A return value of 0 typically means that the underlying object is no longer able to accept bytes and will likely not be able to in the future as well, or that the buffer provided is empty.

How about disconnecting the socket if the write function returns 0?

https://doc.rust-lang.org/std/io/trait.Write.html

When I tested the situation, the write call emits "Broken Pipe" error. I'll check it more.

[majecty]

I found this article from ibm.com
https://developer.ibm.com/technologies/linux/tutorials/l-sockpit/

The closure of a peer socket can also be detected with the write API function. In this case, you’ll receive a SIGPIPE signal or, if this signal is blocked, the write function will return a -1 and set errno to EPIPE.

[majecty]

@MSNTCS This RP fixes the mio issue.

[majecty]

@sgkim126 I'm ready for your review.