Java non-blocking socket write

Question

I'm looking for suggestions for non-blocking socket writes in Java. My code just needs to write some data out to a socket and completely forget about it. I don't care about the response or when the data is actually consumed. What's the best way to do this?

Answer 1

Best idea when you get into complexities like this is to use a networking library like KryoNet (more complex, more features) or PryoNet (less complex, less features) which both support simple asynchronous I/O over sockets. You can pick them apart to understand how they work, if you really want to. Note that a write on a Socket only blocks if the send buffer is full.

If you don't take this route, to handle this simple case without thread synchronisation you need to use Selectors and Channels , as there's no way of easily ascertaining without a busy loop if a socket is 'writeable' at any point in time with no buffer fill level notification mechanism in the basic Socket class. You could also use the socket in a thread, then it can block indefinitely without a problem, but then you may have some synchronisation issues.

Answer 2

Sounds to me like you're after asynchronous I/O. Here is a short example:

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.AsynchronousSocketChannel;
import java.nio.channels.CompletionHandler;

public class Test
{
    public static void main(String[] args)
    {
        final AsynchronousSocketChannel out = AsynchronousSocketChannel.open();
        out.connect(new InetSocketAddress("www.google.com", 80), null,
            new CompletionHandler<Void, Void>()
            {
                @Override
                public void completed(Void result, Void attachment)
                {
                    ByteBuffer buffer = ByteBuffer.allocate(1024);
                    buffer.asCharBuffer().put("GET /index.html HTTP/1.1");
                    out.write(buffer, null, new CompletionHandler<Integer, Void>()
                    {
                        @Override
                        public void completed(Integer result, Void attachment)
                        {
                            // ignore the result
                        }
                            @Override
                        public void failed(Throwable t, Void attachment)
                        {
                            t.printStackTrace();
                        }
                    });
                }

                @Override
                public void failed(Throwable t, Void attachment)
                {
                    t.printStackTrace();
                }
            });
    }
}

You don't need any fancy frameworks. Java7 asynchronous sockets are quite easy to use.

Answer 3

创建一个发布这些事件的线程，它将运行它的后台并将数据提交给服务器。

Answer 4

您可以使用Java NIO的选择器和通道（复杂） - 或者您可以尝试更友好的网络库，如Apache MINA ，它支持非阻塞I / O.