緊跟前文，先把前面缺的例子補(bǔ)全涨颜，接著一步一步分析项滑。
這里的內(nèi)容比較少依沮，直接以注釋的形式補(bǔ)充在每一行上，有必要的地方會(huì)在底下補(bǔ)上圖文枪狂。

public void dispatch(SelectionKey key) throws IOException, InterruptedException {
        if (key.isAcceptable()) {
//前文中已經(jīng)輪訓(xùn)過一遍updateList危喉，通過
//ski.channel.translateAndSetReadyOps已經(jīng)將準(zhǔn)備好的操作set到key中，
//這里的key有4種操作OP_READ州疾，OP_WRITE辜限，OP_CONNECT，OP_ACCEPT严蓖，
//這里只有ServerSocketChannel支持accept操作薄嫡，對(duì)應(yīng)的操作如最底下
            ServerSocketChannel ssc = (ServerSocketChannel) key.channel();
//accept操作必定是ServerSocketChannel
            // 接受一個(gè)連接. 底下詳細(xì)講
            SocketChannel sc = ssc.accept();
            
            // 對(duì)新的連接的channel注冊(cè)read事件. 
            sc.configureBlocking(false);    
                            //這里的selector是另一個(gè)了
            sc.register(readBell.getSelector(), SelectionKey.OP_READ);
            
            // 如果讀取線程還沒有啟動(dòng),那就啟動(dòng)一個(gè)讀取線程.
            synchronized(NioServer.this) {
                if (!NioServer.this.isReadBellRunning) {
                    NioServer.this.isReadBellRunning = true;
                    new Thread(readBell).start();
                }
            }
            
        } else if (key.isReadable()) {
            // 這是一個(gè)read事件,并且這個(gè)事件是注冊(cè)在socketchannel上的.
            SocketChannel sc = (SocketChannel) key.channel(); //這個(gè)channel就是 ssc.accept()對(duì)應(yīng)的那個(gè)
            // 寫數(shù)據(jù)到buffer
            int count = sc.read(temp);
            if (count < 0) {
                // 客戶端已經(jīng)斷開連接.
                key.cancel();
                sc.close();
                return;
            }
            // 切換buffer到讀狀態(tài),內(nèi)部指針歸位.
            temp.flip();
            String msg = Charset.forName("UTF-8").decode(temp).toString();
            System.out.println("Server received ["+msg+"] from client address:" + sc.getRemoteAddress());
            
            Thread.sleep(1000);
            // echo back.
            sc.write(ByteBuffer.wrap(msg.getBytes(Charset.forName("UTF-8"))));
            
            // 清空buffer
            temp.clear();
        }
    }
    
}

核心語句 ssc.accept()

public SocketChannel accept() throws IOException {
    synchronized (lock) {//加鎖
        if (!isOpen())
            throw new ClosedChannelException();
        if (!isBound())
            throw new NotYetBoundException();
        SocketChannel sc = null;

        int n = 0;
        FileDescriptor newfd = new FileDescriptor();
        InetSocketAddress[] isaa = new InetSocketAddress[1];

        try {
            begin();//和下面的end()配對(duì)，用于線程被中斷時(shí)關(guān)閉channel,這里另開一篇再講
            if (!isOpen())
                return null;
            thread = NativeThread.current();
            for (;;) {
                n = accept0(this.fd, newfd, isaa);//native函數(shù)颗胡，解釋：
    // Accepts a new connection, setting the given file descriptor to refer to
    // the new socket and setting isaa[0] to the socket's remote address.
    // Returns 1 on success, or IOStatus.UNAVAILABLE (if non-blocking and no
    // connections are pending) or IOStatus.INTERRUPTED.

                if ((n == IOStatus.INTERRUPTED) && isOpen())//如果狀態(tài)是INTERRUPTED且channel還是open的則繼續(xù)嘗試
                    continue;
                break;
            }
        } finally {
            thread = 0;
            end(n > 0);
            assert IOStatus.check(n);
        }

        if (n < 1)
            return null;

        IOUtil.configureBlocking(newfd, true);
        InetSocketAddress isa = isaa[0];
        //新建一個(gè)socketchannel供read/write操作使用
        sc = new SocketChannelImpl(provider(), newfd, isa);
        //IP端口權(quán)限檢測(cè)
        SecurityManager sm = System.getSecurityManager();
        if (sm != null) {
            try {
                sm.checkAccept(isa.getAddress().getHostAddress(),
                               isa.getPort());
            } catch (SecurityException x) {
                sc.close();
                throw x;
            }
        }
        return sc;

    }
}

就緒操作與通道對(duì)應(yīng)關(guān)系：