java - 这里的SocketChannel为什么不可读？

Question

RT

@Test
    public void channelTest() throws IOException{
        SocketChannel client = SocketChannel.open();
        //Attention here:
        //local connection is established immediately so connectionPending is false here
        System.out.println("is connection pending:"+client.isConnectionPending());
        client.connect(new InetSocketAddress("localhost", 8000));
        client.configureBlocking(false);
        client.write(ByteBuffer.wrap("hello".getBytes()));
        ByteBuffer bf  = ByteBuffer.allocate(5);
        client.read(bf);
        System.out.println(bf);
        //pending means is going to be connected but has not been connected
        //Tells whether or not a connection operation is in progress on this channel.
        System.out.println("is connection pending:"+client.isConnectionPending());
        System.out.println("is connected:"+client.isConnected());
        
        // no need to put finishConnect if connection is on this computer
        //    client1.finishConnect();
        System.out.println("if client1 finished connecting:"+client.isConnected());
    
        Selector selector = Selector.open();
        client.register(selector, SelectionKey.OP_WRITE|SelectionKey.OP_READ|SelectionKey.OP_CONNECT);
        
        //selector has a set of ready channels
        int readyChannels = selector.select();
        System.out.println("ready channels:"+readyChannels);
        Iterator<SelectionKey> keyIter = selector.selectedKeys().iterator();
        
        while(keyIter.hasNext()){
            SelectionKey key = keyIter.next();
            //SocketChannel sc = (SocketChannel) key.channel();
        //    sc.write(ByteBuffer.wrap("hello".getBytes()));
            System.out.println("interest ops:"+key.interestOps());
            System.out.println("ready ops:"+key.readyOps());
            keyIter.remove();
            if(key.isAcceptable()){
                System.out.println("acceptable");
                System.out.println((key.readyOps()&SelectionKey.OP_ACCEPT)!=0);
            }
             if(key.isReadable()){
                System.out.println("readable");
                System.out.println((key.readyOps()&SelectionKey.OP_READ)!=0);
            }
             if(key.isWritable()){
                 System.out.println("writable");
                 System.out.println((key.readyOps()&SelectionKey.OP_WRITE)!=0);
             }
             if(key.isConnectable()){
                System.out.println("connectable");
                System.out.println((key.readyOps()&SelectionKey.OP_CONNECT)!=0);
            }
            
        }
        
    
    }

输出为

is connection pending:false
java.nio.HeapByteBuffer[pos=0 lim=5 cap=5]
is connection pending:false
is connected:true
if client1 finished connecting:true
ready channels:1
interest ops:13
ready ops:4
writable
true