Re: Patch: fix non-blocking socket connect

[Anthony Green <green at redhat dot com>]

On Tue, 2005-12-27 at 01:21 -0700, Tom Tromey wrote:
> In Azureus what happens is that we don't connect within the timeout
> period, so we throw an exception.  However, the OS continues to try to
> connect, since we haven't told it to stop.  Then later some other code
> sees that we've connected and gets confused since the socket's address
> is not set... hence this patch, which sets the address.  But I think
> this patch is most likely incorrect.

Incorrect?  Really?

> One final option is that I'm misinterpreting the Java API and that we
> really are supposed to set nonblocking mode and magically connect
> after Socket.connect has returned.  This seems crazy, but I suppose it
> isn't completely impossible.  A test is needed.

>From Stanley Brown's September '94 post.  You need my Classpath
OP_CONNECT patch to make it work.

Note that it's SocketChannel.connect() that returns early, but it does
this by calling SocketImpl.connect() with a short timeout value (50),
catching the timeout exception, and then checking for the fd in
Selector.select() since we did the  original connect in non-blocking
mode.


import java.net.InetSocketAddress;
import java.nio.channels.*;
import java.util.Iterator;

public class TestConnect
{
  public TestConnect()
  {
    try
      {
	Selector selector = Selector.open();
	SocketChannel channel = SocketChannel.open();
	channel.configureBlocking(false);
	channel.connect(new InetSocketAddress("gcc.gnu.org", 80));
	channel.register(selector, SelectionKey.OP_CONNECT);
	while (true)
	  {
	    selector.select();
	    Iterator it = selector.selectedKeys().iterator();
	    while (it.hasNext())
	      {
		SelectionKey selKey = (SelectionKey)it.next();
		if (selKey.isConnectable())
		  {
		    System.out.println("Connection ready");
		    System.exit(0);
		  }
	      }
	  }
      }
    catch (Exception ex)
      {
	ex.printStackTrace();
      }
  }
  public static void main(String[] args)
  {
    new TestConnect();
  }
}