Java NIO 中的阻塞和非阻塞模式

Question

I'm self-taught Java and I'm a bit confused when implementing this functionality of Java NIO. I am confused about Java NIO's blocking mode. Is the purpose of setting non-blocking mode to be for the selector to detect that the channel is ready for I/O operations? And assuming mode is set to "true" will the selector detect the channel or not? Hoping someone can explain it to me, give me sample code or any suggestions I would be very grateful. Thanks very much

public class NioServer {

public void start() throws IOException {

    Selector selector = Selector.open();

    ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();

    serverSocketChannel.bind(new InetSocketAddress(8000));

    // configureBlocking is problem
    serverSocketChannel.configureBlocking(false);
    ....
    }

Answer 1

In Blocking mode when client communicates with the server call such as send, receive, connect(TCP only) and accept(TCP only) will block indefinitely until that operation is performed. On the other hand in Non Blocking mode these functions will return immediately.

For example, when a client invokes the read() method to read data from the server, the thread gets blocked until the data is available. This situation is undesirable under some circumstances. Instead, what we can do is use the waiting period to do some other task. The client socket then can notify when the data is available. Another problem is that, in a multi-socket connection, each client is a separate thread. Therefore, there is an overhead of maintaining a pool of client threads.

Now to answer your question, you can control whether you want Blocking or Non Blocking mode in your application. If you set like below

  serverSocketChannel.configureBlocking(false);

then server will run in Non Blocking mode otherwise it will run in Blocking mode by default.

Here are some articles for refernece

1. Blocking and Non-Blocking Sockets
2. Non-blocking Socket Programming in Java