问题描述：

服务端已启动，端口9999。

客户端通过Channel方式实现，功能一切正常。

客户端通过Selector+Channel方式实现，程序报错。

哪位兄台遇到过此问题，请赐教

Exception in thread "main" java.nio.channels.NotYetConnectedException

at sun.nio.ch.SocketChannelImpl.ensureWriteOpen(SocketChannelImpl.java:269)

at sun.nio.ch.SocketChannelImpl.write(SocketChannelImpl.java:474)

at demo.nio.SelectorDemo.run(SelectorDemo.java:55)

at demo.nio.SelectorDemo.main(SelectorDemo.java:24)

服务端代码：

package demo.nio;

import java.io.IOException;

import java.net.InetSocketAddress;

import java.nio.ByteBuffer;

import java.nio.channels.ServerSocketChannel;

import java.nio.channels.SocketChannel;

/**

* @ClassName: ServerSocketChannel

* @Description:

* @author

* @date 2018年1月24日 下午9:53:15

*

*/

public class ServerSocketChannelDemo implements Runnable {

public static void main(String[] args) {

ServerSocketChannelDemo serverSocketChannelDemo = new ServerSocketChannelDemo();

serverSocketChannelDemo.run();

}

public void run() {

try {

ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();

serverSocketChannel.socket().bind(new InetSocketAddress(9999));

serverSocketChannel.configureBlocking(false);

while(true){

SocketChannel socketChannel = serverSocketChannel.accept();

if(socketChannel != null){

//do something with socketChannel...

ByteBuffer buf1 = ByteBuffer.allocate(10000);

socketChannel.read(buf1);

buf1.flip();

if(buf1.hasRemaining())

System.out.println(">>>服务端收到数据："+new String(buf1.array()));

buf1.clear();

ByteBuffer buf2 = ByteBuffer.allocate(10000);

buf2.put("A word from server!".getBytes());

buf2.flip();

socketChannel.write(buf2);

socketChannel.close();

}else{

Thread.sleep(3000);

}

}

} catch (IOException e) {

e.printStackTrace();

} catch (InterruptedException e) {

e.printStackTrace();

}

}

}

客户端代码(Channel实现)：

package demo.nio;

import java.io.IOException;

import java.net.InetSocketAddress;

import java.nio.ByteBuffer;

import java.nio.channels.SelectionKey;

import java.nio.channels.Selector;

import java.nio.channels.SocketChannel;

/**

* @ClassName: SocketChannelDemo

* @Description:

* @author

* @date 2018年1月11日 下午10:01:40

*

*/

public class SocketChannelDemo implements Runnable{

public static void main(String[] args) {

SocketChannelDemo socketChannelDemo = new SocketChannelDemo();

socketChannelDemo.run();

}

public void run() {

try {

//通道

SocketChannel socketChannel = SocketChannel.open();

socketChannel.connect(new InetSocketAddress("127.0.0.1", 9999));

while(!socketChannel.finishConnect()){

wait(1000);

}

//缓冲区

ByteBuffer buf1 = ByteBuffer.allocate(10000);

buf1.put("A word from client!".getBytes());

buf1.flip();

if(buf1.hasRemaining())

socketChannel.write(buf1);

buf1.clear();

ByteBuffer buf2 = ByteBuffer.allocate(10000);

socketChannel.read(buf2);

if(buf2.hasRemaining())

System.out.println(">>>客户端接收数据："+new String(buf2.array()));

buf2.clear();

socketChannel.close();

} catch (IOException e) {

e.printStackTrace();

} catch (InterruptedException e) {

e.printStackTrace();

}

}

}

客户端代码(Selector+Channel实现)：

package demo.nio;

import java.io.IOException;

import java.net.InetSocketAddress;

import java.nio.ByteBuffer;

import java.nio.channels.SelectableChannel;

import java.nio.channels.SelectionKey;

import java.nio.channels.Selector;

import java.nio.channels.ServerSocketChannel;

import java.nio.channels.SocketChannel;

import java.util.Set;

import java.util.Iterator;

/**

* @ClassName: SelectorDemo

* @Description:

* @author

* @date 2018年1月12日 下午9:06:21

*

*/

public class SelectorDemo implements Runnable{

public static void main(String[] args) {

SelectorDemo selectorDemo = new SelectorDemo();

selectorDemo.run();

}

public void run() {

try {

//选择器

Selector selector = Selector.open();

//通道

SocketChannel socketChannel1 = SocketChannel.open();

socketChannel1.configureBlocking(false);

SelectionKey key1 = socketChannel1.register(selector, SelectionKey.OP_CONNECT);

socketChannel1.connect(new InetSocketAddress("127.0.0.1", 9999));

while(true){

int readyChannels = selector.selectNow();//selectNow()非阻塞，select(timeout)和select()阻塞

if(readyChannels == 0)

continue;

//selector.wakeup();//第一个线程调用select后，需要执行此方法，阻塞在select上的线程会立马返回。

Set> selectedKeys = selector.selectedKeys();

Iterator> keyIterator = selectedKeys.iterator();

while(keyIterator.hasNext()){

SelectionKey key = (SelectionKey) keyIterator.next();

if(key.isAcceptable()){

// a connection was accepted by a ServerSocketChannel.

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

}else if(key.isConnectable()){

// a connection was established with a remote server.

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

ByteBuffer buf1 = ByteBuffer.allocate(10000);

buf1.put("A word from client!".getBytes());

buf1.flip();

socketchannel.write(buf1);

buf1.clear();

ByteBuffer buf2 = ByteBuffer.allocate(10000);

socketchannel.read(buf2);

buf2.flip();

System.out.println(">>>客户端接收数据："+new String(buf2.array()));

buf2.clear();

}else if(key.isReadable()){

// a channel is ready for reading.

SelectableChannel fileChannel = key.channel();

}else if(key.isWritable()){

// a channel is ready for writing.

SelectableChannel fileChannel = key.channel();

}

keyIterator.remove();

}

}

} catch (IOException e) {

e.printStackTrace();

}

}

}