How to handle write errors in non blocking sockets

Hi,
I'm using sockets registered with a Selector for read operations. I've seen code examples that put the SocketChannel in non blocking mode before registering it with the selector, and in fact not doing so would cause an IllegalBlockingModeException to be thrown.
My problem is that I can't handle write errors. The call to write() returns inmediately without throwing any exception. Even worse, when the network timeout expires the selector wakes up and I get an exception on read(). So I can't tell the difference between a real read error and a write error.
What can I do? Is there a magic method I haven't heard about?
Thanks

ejp wrote:
OK, so what happens is this: you write from your ByteBuffer; if there is room in the socket send buffer, the data is transferred and the transfer count is returned. (If there isn''t, the write returns zero and nothing has happened.) Your application code then continues. Meanwhile TCP is trying to send the data in the send buffer and get an ACK from the peer. If the peer is down as per your test, eventually those write attempts will time out. You will then get a connection reset exception on the next read or write.
Even worse, when the network timeout expires the selector wakes upCorrect, to tell you there is an error condition pending. This is good, not bad.You're right. This way my program can know that something happened.
But I still don't understand what the difference between a failed write() and a failed read() is. I mean, the error condition may appear during a send attempt, or it may appear after sending. In both cases I get an error when trying to read. How can my program know if data have been received by the other end?
Do I have to implement ACK messages in the application level protocol??? It'd be nice if TCP could do this for me...

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