NIO服务端和客户端通信demo

package nio;

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.*;
import java.util.concurrent.ConcurrentHashMap;

public class Server {
private Selector selector;
private ByteBuffer readBuffer = ByteBuffer.allocate(1024);//调整缓存的大小可以看到打印输出的变化
private ByteBuffer sendBuffer = ByteBuffer.allocate(1024);//调整缓存的大小可以看到打印输出的变化

String str;
public void start() throws IOException {
// 打开服务器套接字通道
ServerSocketChannel ssc = ServerSocketChannel.open();
// 服务器配置为非阻塞
ssc.configureBlocking(false);
// 进行服务的绑定
ssc.bind(new InetSocketAddress("localhost", 8001));

// 通过open()方法找到Selector
selector = Selector.open();
// 注册到selector，等待连接
ssc.register(selector, SelectionKey.OP_ACCEPT);

while (!Thread.currentThread().isInterrupted()) {
selector.select();
Set<SelectionKey> keys = selector.selectedKeys();
Iterator<SelectionKey> keyIterator = keys.iterator();
while (keyIterator.hasNext()) {
SelectionKey key = keyIterator.next();
if (!key.isValid()) {
continue;
}
if (key.isAcceptable()) {
accept(key);
} else if (key.isReadable()) {
read(key);
} else if (key.isWritable()) {
write(key);
}
keyIterator.remove(); //该事件已经处理，可以丢弃
}
}
}

private void write(SelectionKey key) throws IOException, ClosedChannelException {
SocketChannel channel = (SocketChannel) key.channel();
System.out.println("write:"+str);

sendBuffer.clear();
sendBuffer.put(str.getBytes());
sendBuffer.flip();
channel.write(sendBuffer);
channel.register(selector, SelectionKey.OP_READ);
}

private void read(SelectionKey key) throws IOException {
SocketChannel socketChannel = (SocketChannel) key.channel();

// Clear out our read buffer so it's ready for new data
this.readBuffer.clear();
//        readBuffer.flip();
// Attempt to read off the channel
int numRead;
try {
numRead = socketChannel.read(this.readBuffer);
} catch (IOException e) {
// The remote forcibly closed the connection, cancel
// the selection key and close the channel.
key.cancel();
socketChannel.close();

return;
}

str = new String(readBuffer.array(), 0, numRead);
System.out.println(str);
socketChannel.register(selector, SelectionKey.OP_WRITE);
}

private void accept(SelectionKey key) throws IOException {
ServerSocketChannel ssc = (ServerSocketChannel) key.channel();
SocketChannel clientChannel = ssc.accept();
clientChannel.configureBlocking(false);
clientChannel.register(selector, SelectionKey.OP_READ);
System.out.println("a new client connected "+clientChannel.getRemoteAddress());
}

public static void main(String[] args) throws IOException {
System.out.println("server started...");
new Server().start();
}
}

作者：御风逍遥
链接：https://www.jianshu.com/p/a9d030fec081
來源：简书
著作权归作者所有。商业转载请联系作者获得授权，非商业转载请注明出处。

package 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;
import java.util.Iterator;
import java.util.Scanner;
import java.util.Set;

public class Client {

ByteBuffer writeBuffer = ByteBuffer.allocate(1024);
ByteBuffer readBuffer = ByteBuffer.allocate(1024);

public void start() throws IOException {
// 打开socket通道
SocketChannel sc = SocketChannel.open();
//设置为非阻塞
sc.configureBlocking(false);
//连接服务器地址和端口
sc.connect(new InetSocketAddress("localhost", 8001));
//打开选择器
Selector selector = Selector.open();
//注册连接服务器socket的动作
sc.register(selector, SelectionKey.OP_CONNECT);

Scanner scanner = new Scanner(System.in);
while (true) {
//选择一组键，其相应的通道已为 I/O 操作准备就绪。
//此方法执行处于阻塞模式的选择操作。
selector.select();
//返回此选择器的已选择键集。
Set<SelectionKey> keys = selector.selectedKeys();
System.out.println("keys=" + keys.size());
Iterator<SelectionKey> keyIterator = keys.iterator();
while (keyIterator.hasNext()) {
SelectionKey key = keyIterator.next();
keyIterator.remove();
// 判断此通道上是否正在进行连接操作。
if (key.isConnectable()) {
sc.finishConnect();
sc.register(selector, SelectionKey.OP_WRITE);
System.out.println("server connected...");
break;
} else if (key.isWritable()) { //写数据
System.out.print("please input message:");
String message = scanner.nextLine();
//ByteBuffer writeBuffer = ByteBuffer.wrap(message.getBytes());
writeBuffer.clear();
writeBuffer.put(message.getBytes());
//将缓冲区各标志复位,因为向里面put了数据标志被改变要想从中读取数据发向服务器,就要复位
writeBuffer.flip();
sc.write(writeBuffer);

//注册写操作,每个chanel只能注册一个操作，最后注册的一个生效
//如果你对不止一种事件感兴趣，那么可以用“位或”操作符将常量连接起来
//int interestSet = SelectionKey.OP_READ | SelectionKey.OP_WRITE;
//使用interest集合
sc.register(selector, SelectionKey.OP_READ);
sc.register(selector, SelectionKey.OP_WRITE);
sc.register(selector, SelectionKey.OP_READ);

} else if (key.isReadable()){//读取数据
System.out.print("receive message:");
SocketChannel client = (SocketChannel) key.channel();
//将缓冲区清空以备下次读取
readBuffer.clear();
int num = client.read(readBuffer);
System.out.println(new String(readBuffer.array(),0, num));
//注册读操作，下一次读取
sc.register(selector, SelectionKey.OP_WRITE);
}
}
}
}

public static void main(String[] args) throws IOException {
new Client().start();
}
}

作者：御风逍遥
链接：https://www.jianshu.com/p/a9d030fec081
來源：简书
著作权归作者所有。商业转载请联系作者获得授权，非商业转载请注明出处。