Selector in NIO notifies data to be read but bytes read 0

Question

Hi All,
I am facing a problem in NIO which for which I have clue.
The selector object notifies that data is ready to be read from a particular channel after which
I execute the following to read the data into the buffer
readBuffer.clear();
int count = this.sockChannel.read(this.readBuffer);
The value of count which i get is 0 after which which i return without any processing
but this notification goes on and on as I can see in the logs which goes on logging
Count received as 0 infinitely.
Please help

Answer 1

There's a few things here.
1. I prefer to see only one read statement in these loops, like this:
while ((count = in.read(readBuffer)) > 0)
  readBuffer.flip();
  // get() from readBuffer into somewhere
// NB the 'len' to use is 'count'. You don't need to get it again via 'position()'.
// it generally makes more sense to use compact rather than clear() here
  readBuffer.compact();
}2. count < 0 doesn' t mean the socket is closed, it means the connection is closed. You have to close the socket, or the channel, yourself, and I don't see that:
if (count < 0)
  logger.debug("connection closed" ...); // etc
  in.close();
}3. You're testing bytes.length > 0 in a place where it can't possibly be zero.
4. I hope you're not really ignoring exceptions as shown. If you are, that would explain the behaviour completely - never do that. If you get any kind of an IOException in this code, the connection is hosed and you must log the exception and close the channel. The only exception to this rule is SocketTimeoutException, which doesn't happen in non-blocking mode.
5. Is there any possibility that the buffer is zero length? That would cause read() to return zero.