Question

我是Java NIO的新手，在阅读了一些教程之后，我已经尝试了自己编写一个简单的NIO服务器和客户端。我的服务器只是做一件简单的事情就是从客户端监听并打印到控制台，客户端只是连接到服务器并发送3条消息“Hello”。问题是我的服务器监听并正常处理3条消息，之后它应该被阻止并继续监听，但它没有，没有阻塞，它在无限循环时运行它。这是我的服务器和客户端：

服务器

import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;
import java.util.Iterator;
import java.util.Set;

public class Server {
    public static void main(String args[]) throws Exception {
        // Create the server socket channel
        ServerSocketChannel server = ServerSocketChannel.open();
        // nonblocking I/O
        server.configureBlocking(false);
        // host-port 8000
        server.socket().bind(new InetSocketAddress(8000));
        System.out.println("Server actives at port 8000");
        // Create the selector
        Selector selector = Selector.open();
        // Recording server to selector (type OP_ACCEPT)
        server.register(selector, SelectionKey.OP_ACCEPT);

        while (selector.select() > 0) {

            // Get keys
            Set<SelectionKey> keys = selector.selectedKeys();
            Iterator<SelectionKey> i = keys.iterator();

            // print 
            System.out.println("[ " + keys.size() + " ]");

            // For each keys...
            while (i.hasNext()) {
                SelectionKey key = (SelectionKey) i.next();
                // Remove the current key
                i.remove();

                // if isAccetable = true
                // then a client required a connection
                if (key.isAcceptable()) {
                    // get client socket channel
                    SocketChannel client = server.accept();
                    // Non Blocking I/O
                    client.configureBlocking(false);
                    // recording to the selector (reading)
                    client.register(selector, SelectionKey.OP_READ);
                    continue;
                }

                // if isReadable = true
                // then the server is ready to read
                if (key.isReadable()) {

                    SocketChannel client = (SocketChannel) key.channel();

                    // Read byte coming from the client
                    int BUFFER_SIZE = 1024;
                    ByteBuffer buffer = ByteBuffer.allocate(BUFFER_SIZE);
                    try {
                        client.read(buffer);
                    } catch (Exception e) {
                        // client is no longer active
                        e.printStackTrace();
                    }

                    // Show bytes on the console
                    buffer.flip();
                    Charset charset = Charset.forName("ISO-8859-1");
                    CharsetDecoder decoder = charset.newDecoder();
                    CharBuffer charBuffer = decoder.decode(buffer);
                    System.out.println("[" + charBuffer.toString() + "]");
                }
            }
        }
    }
}

这是我的客户：

import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.SocketChannel;
import java.util.Iterator;
import java.util.Set;

public class Client {
    public static void main(String args[]) throws Exception {
        // Create client SocketChannel
        SocketChannel client = SocketChannel.open();

        // nonblocking I/O
        client.configureBlocking(false);

        // Connection to host port 8000
        client.connect(new java.net.InetSocketAddress("127.0.0.1", 8000));

        // Create selector
        Selector selector = Selector.open();

        // Record to selector (OP_CONNECT type)
        SelectionKey clientKey = client.register(selector,
                SelectionKey.OP_CONNECT);

        int counter = 0;
        boolean chk = true;

        // Waiting for the connection
        while (selector.select(500) > 0 && chk) {
            // Get keys
            Set<SelectionKey> keys = selector.selectedKeys();
            Iterator<SelectionKey> i = keys.iterator();

            // For each key...
            while (i.hasNext() && chk) {
                SelectionKey key = (SelectionKey) i.next();

                // Remove the current key
                i.remove();

                // Get the socket channel held by the key
                SocketChannel channel = (SocketChannel) key.channel();

                // Attempt a connection
                if (key.isConnectable()) {

                    // Connection OK
                    System.out.println("Server Found");

                    // Close pendent connections
                    if (channel.isConnectionPending())
                        channel.finishConnect();

                    // Write continuously on the buffer
                    ByteBuffer buffer = null;
                    for (;chk;counter++) {
                        Thread.sleep(1000);
                        buffer = ByteBuffer.wrap(new String(" Client ").getBytes());
                        channel.write(buffer);
                        buffer.clear();

                        if (counter == 2)
                        {
                             chk = false;
                             client.close();
                        }
                    }

                }
            }
        }
    }
}

任何人都可以解释我的代码有什么问题？提前谢谢。

Answer 1

您可能会从接受的套接字通道中获得源源不断的EOS-s。你忽略了read()的结果。你必须至少检查它是否为-1，如果是这样，请关闭频道。

Answer 2

NIO套接字apis是非阻塞的。选择器返回准备好操作的键。如果没有任何准备就绪，那么它将继续循环。这是预期的行为。

Answer 3

因

而没有阻止

server.configureBlocking(false);

在Server.main（）

中

带有Selector的无限循环，即使客户端没有连接

3 个答案: