在做关于NIO TCP编程小案例时遇到无法监听write的问题，没想到只是我的if语句的位置放错了位置，哎，看了半天没看出来
贴下课堂笔记：
在Java中使用NIO进行网络TCP套接字编程主要以下几个类：
ServerSocketChannel: 服务端套接字通道,主要监听接收客户端请求
Selector：通道选择器,主要用于管理服务端通道和所有客户端通道(监听通道中发生的事件)，也就说是一个多路通道复用器。
SelectorKey: 事件选择键
SocketChannel: 套接字通道(客户端)
这篇文章《NIO编程中的SelectionKey.interestOps方法中的逻辑运算》解决了我一些疑问，地址:https://blog.csdn.net/woaiqianzhige/article/details/78696188
NIO 套接字服务端开发步骤：
- 创建选择器
- 启动服务端通道
- 设置服务端通道为非阻塞模式
- 将服务端通道注册到选择器
- 轮训通道事件
- 处理通道事件
- 关闭通道(可选)
案例：服务端接收客户端发送的短信息，服务端回复已收到。
服务端代码：
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.ClosedChannelException;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.util.Iterator;
import java.util.Set; public class Server {
private Selector selector;
private ServerSocketChannel serverSocketChannel;
private ByteBuffer byteBuffer = ByteBuffer.allocate(8192); /**
* 构造方法 启动服务器
*
* @param port
* @throws IOException
*/
public Server() {
try {
selector = Selector.open();
serverSocketChannel = ServerSocketChannel.open();
serverSocketChannel.configureBlocking(false);
serverSocketChannel.bind(new InetSocketAddress(10086));
serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
System.out.println("Server start successful with port: 10086");
} catch (ClosedChannelException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
} public static void main(String[] args) throws Exception {
new Server().start();
} private void start() {
while (true) {
try {
selector.select();
Set<SelectionKey> keys = selector.selectedKeys();
Iterator<SelectionKey> keyIterator = keys.iterator();
while (keyIterator.hasNext()) {
SelectionKey key = keyIterator.next();
keyIterator.remove();
if (!key.isValid()) {
continue;
}
if (key.isAcceptable()) {
accept(key);
}
if (key.isReadable()) {
receive(key);
}
if (key.isWritable()) {
reply(key);
}
}
} catch (IOException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
}
} private void reply(SelectionKey key) {
try {
SocketChannel socketChannel = (SocketChannel) key.channel();
byteBuffer.clear();
String message = "receive success";
byteBuffer.put(message.getBytes());
byteBuffer.flip();
socketChannel.write(byteBuffer);
System.out.println("reply:" + message);
byteBuffer.clear();
key.interestOps(SelectionKey.OP_READ);
} catch (IOException e) {
e.printStackTrace();
}
} private void receive(SelectionKey key) {
try {
SocketChannel socketChannel = (SocketChannel) key.channel();
byteBuffer.clear();
int flag = socketChannel.read(byteBuffer);
if (flag == -1) {
key.channel().close();
key.cancel();
return;
}
byteBuffer.flip();
byte[] buf = new byte[byteBuffer.remaining()];
byteBuffer.get(buf);
String message = new String(buf);
System.out.println("receive message:" + message);
byteBuffer.clear();
key.interestOps(SelectionKey.OP_WRITE);
} catch (IOException e) {
e.printStackTrace();
}
} private void accept(SelectionKey key) {
try {
SocketChannel socketChannel = serverSocketChannel.accept();
socketChannel.configureBlocking(false);
socketChannel.register(selector, SelectionKey.OP_READ | SelectionKey.OP_WRITE);
System.out.println(Thread.currentThread().getName() + ": create client channel.");
} catch (ClosedChannelException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
客户端代码：
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.ClosedChannelException;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.SocketChannel;
import java.util.Iterator;
import java.util.Scanner; public class Client {
private Selector selector;
private ByteBuffer byteBuffer = ByteBuffer.allocate(1024);
private SocketChannel socketChannel; public Client() {
try {
selector = Selector.open();
socketChannel = SocketChannel.open();
socketChannel.configureBlocking(false);
socketChannel.register(selector, SelectionKey.OP_CONNECT | SelectionKey.OP_READ | SelectionKey.OP_WRITE);
socketChannel.connect(new InetSocketAddress("127.0.0.1", 10086));
System.out.println("Client start successful");
} catch (ClosedChannelException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
} public static void main(String[] args) {
new Client().start();
} private void start() {
while (true) {
try {
selector.select();
Iterator<SelectionKey> keys = selector.selectedKeys().iterator();
while (keys.hasNext()) {
SelectionKey key = keys.next();
keys.remove();
if (!key.isValid()) {
continue;
}
if (key.isConnectable()) {
if (socketChannel.finishConnect()) {
key.interestOps(key.interestOps() & ~SelectionKey.OP_CONNECT);
System.out.println("Client connect server success");
}
}
if (key.isReadable()) {
receive(key);
}
if (key.isWritable()) {
reply(key);
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
} private void reply(SelectionKey key) {
try {
@SuppressWarnings("resource")
Scanner scanner = new Scanner(System.in);
byteBuffer.clear();
System.out.println("please input message:");
String message = scanner.next();
byteBuffer.put(message.getBytes());
byteBuffer.flip();
socketChannel.write(byteBuffer);
byteBuffer.clear();
System.out.println("send message:" + message);
key.interestOps(SelectionKey.OP_READ);
} catch (IOException e) {
e.printStackTrace();
}
} private void receive(SelectionKey key) {
try {
byteBuffer.clear();
socketChannel.read(byteBuffer);
byteBuffer.flip();
byte[] bytes = new byte[byteBuffer.remaining()];
byteBuffer.get(bytes);
String message = new String(bytes).trim();
System.out.println("receive message: " + message);
byteBuffer.clear();
key.interestOps(SelectionKey.OP_WRITE);
} catch (IOException e) {
e.printStackTrace();
}
}
}
真是粗心大意了。。。特发此博文给我自己涨涨记性
