问题描述
当我这样编码时:
ServerSocketChannel ssc = ServerSocketChannel.open();
InetSocketAddress sa = new InetSocketAddress("localhost",8888);
ssc.socket().bind(sa);
ssc.configureBlocking(false);
ssc.socket().accept();
ServerSocket.accept()方法抛出java.nio.channels.IllegalBlockingModeException.即使我将阻止设置为false，为什么我也不能呼叫accept()?
the ServerSocket.accept() method throws java.nio.channels.IllegalBlockingModeException. Why can't I call accept(), even though I set blocking to false?
推荐答案
Javadoc特别声明ServerSocketChannel.accept():
The Javadoc specifically states that ServerSocketChannel.accept():
如果此通道处于非阻塞模式，则此方法将立即 如果没有挂起的连接，则返回null.否则会阻塞 无限期地等待新的连接可用或发生I/O错误.
If this channel is in non-blocking mode then this method will immediately return null if there are no pending connections. Otherwise it will block indefinitely until a new connection is available or an I/O error occurs.
总体思路是:
- 如果要在等待传入连接时进行阻止，则将服务器套接字置于阻止模式.如果您要编写的服务器在实际建立连接之前无事可做，则您需要的是阻塞模式.
- 如果您想做其他事情，并定期检查是否有未决的连接，则需要使用非阻塞模式.
默认情况下，阻塞模式是有原因的:大多数服务器不想轮询其接受套接字中的传入连接.
Blocking mode is the default for a reason: Most servers don't want to poll their accepting socket for incoming connections.
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