Java NIO UDP - Selector Hangs when trying to register

final DatagramChannel dc = DatagramChannel.open();
        dc.configureBlocking(false);
        dc.socket().bind(localAddress);
        final SelDatagramChannel c = new SelDatagramChannel(dc, datagramListener);
--->>>>        final SelectionKey sk = dc.register(selector, SelectionKey.OP_READ);

The marke开发者_运维技巧t line hangs forever when you try to register a DatagramChannel.

Does anyone know why?

There's some chat in http://echelog.matzon.dk/logs/browse/java/1276898400 which mentions that dc.register() must be called in the selection thread. The JavaDoc doesn't seem very specific about that, though.

I guess you do that by putting in a list somewhere, and calling selector.wakeup(). But I'm still having timing glitches where it's unclear how long before the register succeeds...

Have you tried sending a CTRL+BREAK to the JVM to get a thread dump ?

Is the above code executed in the thread which does selection? I think we need to register the channels with Selector in the same thread which does selection.