Question

我使用以下代码开发了一个服务器通道套接字：

public class EchoServer {
private static final int BUFFER_SIZE = 1024;

private final static int DEFAULT_PORT = 9090;

private long numMessages = 0;

private long loopTime;

private InetAddress hostAddress = null;

private int port;

private Selector selector;

// The buffer into which we'll read data when it's available
private ByteBuffer readBuffer = ByteBuffer.allocate(BUFFER_SIZE);

int timestamp=0;

public EchoServer() throws IOException {
    this(DEFAULT_PORT);
}

public EchoServer(int port) throws IOException {
    this.port = port;
    hostAddress = InetAddress.getByName("127.0.0.1");
    selector = initSelector();
    loop();
}

private Selector initSelector() throws IOException {
    Selector socketSelector = SelectorProvider.provider().openSelector();

    ServerSocketChannel serverChannel = ServerSocketChannel.open();
    serverChannel.configureBlocking(false);

    InetSocketAddress isa = new InetSocketAddress(hostAddress, port);
    serverChannel.socket().bind(isa);
    serverChannel.register(socketSelector, SelectionKey.OP_ACCEPT);
    return socketSelector;
}

private void loop() {
    for (;true;) {
        try {
            selector.select();
            Iterator<SelectionKey> selectedKeys = selector.selectedKeys()
                    .iterator();
            while (selectedKeys.hasNext()) {
                SelectionKey key = selectedKeys.next();
                selectedKeys.remove();
                if (!key.isValid()) {
                    continue;
                }
                 // Check what event is available and deal with it
                if (key.isAcceptable()) {
                    accept(key);
                } else if (key.isWritable()) {
                    write(key);
                }
            }
            Thread.sleep(3000);
            timestamp+=3;
        } catch (Exception e) {
            e.printStackTrace();
            System.exit(1);
        }



    }
}

private void accept(SelectionKey key) throws IOException {

    ServerSocketChannel serverSocketChannel = (ServerSocketChannel) key.channel();

    SocketChannel socketChannel = serverSocketChannel.accept();
    socketChannel.configureBlocking(false);
    socketChannel.setOption(StandardSocketOptions.SO_KEEPALIVE, true);
    socketChannel.setOption(StandardSocketOptions.TCP_NODELAY, true);
  //  socketChannel.register(selector, SelectionKey.OP_READ);
    socketChannel.register(selector, SelectionKey.OP_WRITE);

    System.out.println("Client is connected");
}

private void write(SelectionKey key) throws IOException {
    SocketChannel socketChannel = (SocketChannel) key.channel();
    ByteBuffer dummyResponse = ByteBuffer.wrap(("ok:" + String.valueOf(timestamp)) .getBytes("UTF-8"));

    socketChannel.write(dummyResponse);
    if (dummyResponse.remaining() > 0) {
        System.err.print("Filled UP");
    }
    System.out.println("Message Sent");
 //   key.interestOps(SelectionKey.OP_READ);
}

}

如您所见，我在localhost端口9090上运行它。为了测试重型连接的代码，我开发了一个测试应用程序，每秒运行一个新线程并连接到服务器。这是我的测试应用程序的代码：

    public class Main {

    /**
     * @param args
     */
    public static void main(String[] args) {
        int i = 0;
        try {
            while (i < 10000) {
                RunnableDemo temp = new RunnableDemo("Thread-"
                        + String.valueOf(i));
                temp.start();
                i++;
                Thread.sleep(1000);
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

class RunnableDemo implements Runnable {
    private Thread t;
    private String threadName;

    InetAddress host = null;
    int port = 9090;

    RunnableDemo(String name) {
        threadName = name;
        System.err.println("Creating " + threadName);

    }

    public void run() {
        System.err.println("Running " + threadName);
        try {
            SocketChannel socketChannel = SocketChannel.open();

            socketChannel.connect(new InetSocketAddress(host, port));

            while (!socketChannel.finishConnect())
                ;

            System.out.println("Thread " + threadName + " Connected");
            ByteBuffer buffer = ByteBuffer.allocate(1024);
            while (true) {
                if (socketChannel.read(buffer) > 0) {
                    buffer.flip();
                    byte[] bytes = new byte[buffer.limit()];
                    buffer.get(bytes);  
                    System.out.println(threadName+ ":" + new String(bytes));
                    buffer.clear();
                }
            }

        } catch (Exception e) {
            System.out.println("Thread " + threadName + " interrupted.");
            e.printStackTrace();
        }
        System.out.println("Thread " + threadName + " exiting.");
    }

    public void start() {
        System.out.println("Starting " + threadName);
        try {
            host = InetAddress.getByName("127.0.0.1");
            if (t == null) {
                t = new Thread(this, threadName);
                t.start();
            }
        } catch (UnknownHostException e) {
            e.printStackTrace();
        }
    }

}

测试应用程序运行但只有75个线程可以连接到服务器，并且第75个之后的所有线程都显示在异常之下：

java.net.ConnectException: Connection refused: connect
at sun.nio.ch.Net.connect0(Native Method)
at sun.nio.ch.Net.connect(Unknown Source)
at sun.nio.ch.Net.connect(Unknown Source)
at sun.nio.ch.SocketChannelImpl.connect(Unknown Source)
at net.behboodi.client.RunnableDemo.run(Main.java:48)
at java.lang.Thread.run(Unknown Source)

对套接字的并发连接数有限制吗？或者使用端口127.0.0.1和本地主机有任何限制吗？另一个想法是，Java应用程序或JVM可能无法创建超过75个线程。

我搜索了所有这些，但没有找到任何答案，告诉我上述原因是我的主要问题是什么以及如何修复代码以便我可以测试超过10000个并发线程的应用程序？

Answer 1

摆脱困境。选择器已经阻塞。睡在网络代码中只是浪费时间。注意（1）你没有在阻塞模式下调用finishConnect()，（2）你没有将线程连接到ServerChannel，你是将客户端套接字连接到服务器套接字，（3）你的客户端代码没有处理流的结束，以及（4）这不是echo服务器。 - EJP

连接75个客户端到服务器后连接被拒绝

1 个答案: