JAVA NIO Selector構建簡單伺服器

• ServerSocketChannel + Selector
• SocketChannel
• UnitTest
• 結果

ServerSocketChannel + Selector

NIOServer.java

public class NIOServer implements Runnable{

    private int clientNum = 0;
    private int bufferSize = 12;

    @Override
    public
 
 void run() {

        try {
            // 建立通道和選擇器
            ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
            Selector selector = Selector.open();
            InetSocketAddress inetSocketAddress = new InetSocketAddress("127.0.0.1", 5500);
            serverSocketChannel.
 
socket().bind(inetSocketAddress);
            // 設定通道非阻塞 繫結選擇器
            serverSocketChannel.configureBlocking(false);
            /*
             * ServerSocketChannel只有accept
             */
            serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT).attach("server");
            System.
 
out.println("Server started .... port:5500");

            while(true) {
                int readyChannels = selector.select();
                if(readyChannels == 0) continue;
                Set selectedKeys = selector.selectedKeys();
                Iterator keyIterator = selectedKeys.iterator();
                while(keyIterator.hasNext()) {

                    SelectionKey key = (SelectionKey)keyIterator.next();
                    // 判斷是哪個事件
                    if(key.isAcceptable()) {// 客戶請求連線
                        System.out.println(key.attachment()+ " - 接受請求事件");
                        ++clientNum;
                        // 獲取通道 接受連線,
                        // 設定非阻塞模式（必須），同時需要註冊 讀寫資料的事件，這樣有訊息觸發時才能捕獲
                        SocketChannel socketChannel = ((ServerSocketChannel) key.channel()).accept();

                        socketChannel.configureBlocking(false);
                        socketChannel.register(selector, SelectionKey.OP_READ).attach("accept"+clientNum);

                        System.out.println(key.attachment() + " - 已連線");
                    } else if (key.isConnectable()) {
                        System.out.println(key.attachment()+ " - 連線事件");
                    } else if (key.isReadable()) {
                        System.out.println(key.attachment()+ " - 讀資料事件");
                        SocketChannel clientChannel=(SocketChannel)key.channel();
                        ByteBuffer receiveBuf = ByteBuffer.allocate(bufferSize);
                        clientChannel.read(receiveBuf);
                        System.out.println(key.attachment()+ " - 讀取資料：" + getString(receiveBuf));
                    } else if (key.isWritable()) {
                        System.out.println(key.attachment()+ " - 寫資料事件");
                        SocketChannel clientChannel = (SocketChannel) key.channel();
                        ByteBuffer sendBuf = ByteBuffer.allocate(bufferSize);
                        String sendText = "helloc";
                        sendBuf.put(sendText.getBytes());
                        sendBuf.flip();        //寫完資料後呼叫此方法
                        clientChannel.write(sendBuf);
                    }
                    keyIterator.remove();
                }
            }

        } catch (Exception e) {
            e.printStackTrace();
        }

    }

    public String getString(ByteBuffer buffer){
        StringBuffer builder = new StringBuffer("");
        try{
            for(int i = 0; i<buffer.position();i++){
                builder.append((char)buffer.get(i));
            }
            return builder.toString();
        }catch (Exception ex){
            ex.printStackTrace();
            return builder.toString();
        }
    }
}

SocketChannel

NIOClient.java

public class NIOClient implements Runnable {

    private String tag = "client";
    private ByteBuffer readBuffer;
    private ByteBuffer writeBuffer;
    private boolean isConnected = false;
    private int bufferSize = 12;

    public NIOClient(String tag){
        this.tag = tag;
        readBuffer = ByteBuffer.allocate(bufferSize);
        writeBuffer = ByteBuffer.allocate(bufferSize);
    }

    @Override
    public void run() {

        try {

            Selector selector = Selector.open();

            SocketChannel socketChannel  = SocketChannel.open();

            socketChannel.configureBlocking(false);
            socketChannel.connect(new InetSocketAddress("127.0.0.1", 5500));
            socketChannel.register(selector, SelectionKey.OP_CONNECT | SelectionKey.OP_READ|SelectionKey.OP_WRITE).attach(tag);

            System.out.println(tag+" connect .... port:5500");

            while(true) {
                int readyChannels = selector.select();
                if(readyChannels == 0) continue;
                Set selectedKeys = selector.selectedKeys();
                Iterator keyIterator = selectedKeys.iterator();
                while(keyIterator.hasNext()) {

                    SelectionKey key = (SelectionKey)keyIterator.next();
                    // 判斷是哪個事件
                    if(key.isAcceptable()) {// 客戶請求連線
                        System.out.println(key.attachment()+ "is accepted by server");

                    } else if (key.isConnectable()) {
                        System.out.println(key.attachment()+ " connect ");
                        SocketChannel channel = (SocketChannel) key.channel();
                        if (channel.isConnectionPending()) {
                            try {
                                /*
                                 * 人為將程式中止，等待連線建立完成,否則會報如下錯誤
                                 * java.nio.channels.NotYetConnectedException at sun.nio.ch.SocketChannelImpl.ensureWriteOpen(SocketChannelImpl.java:274)
                                 */
                                if (channel.finishConnect()) {
                                    System.out.println(key.attachment()+" connect server succ");
                                    isConnected = true;
                                }
                            } catch (IOException e) {
                                e.printStackTrace();
                            }
                        }
                    } else if (key.isReadable()) {
                        System.out.println(key.attachment()+ " read ");

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

                        try {
                            int len = clientChannel.read(readBuffer);
                            if (len == -1) {
                                System.out.println(key.attachment()+" read : len=-1");
                                // 說明連線已經斷開
                                selector.close();
                                socketChannel.close();
                            } else {
                                readBuffer.flip();
                                byte[] buffer = new byte[len];
                                readBuffer.get(buffer);
                                readBuffer.clear();
                                System.out.println(key.attachment()+" read : len=" + len + ", str=" + new String(buffer));
                            }
                        } catch (IOException e) {
                            e.printStackTrace();
                        }

                    } else if (key.isWritable()) {
                        System.out.println(key.attachment()+ " write ");
                        SocketChannel clientChannel = (SocketChannel) key.channel();
                        String str = "hellos";
                        byte[] buffer = str.getBytes();
                        writeBuffer.put(buffer);
                        writeBuffer.flip();
                        try {
                            System.out.println(key.attachment()+ " write : len=" + buffer.length + ", str=" + str);
                            clientChannel.write(writeBuffer);

                            try {
                                Thread.sleep(100);
                            }catch (Exception e){
                                e.printStackTrace();
                            }
                        } catch (IOException e) {
                            e.printStackTrace();
                        }
                        writeBuffer.clear();
                    }
                    keyIterator.remove();
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

}

UnitTest

    @Test
    public void server(){
        Thread server = new Thread(new NIOServer());
        server.start();

        try {
            Thread.sleep(200);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        Thread client1 = new Thread(new NIOClient("client1"));
        client1.start();

        Thread client2 = new Thread(new NIOClient("client2"));
        client2.start();

        try {
            Thread.sleep(300);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }


        client1.stop();
        client2.stop();

        server.stop();
	}

結果