javaNIO的第一个例子
功能描述：一个服务器端，多个客户端，客户端向服务器端发送消息，服务器端转发给所有客户端（包括发送者）。
服务器端代码：
package com.imooc.nio;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.nio.charset.Charset;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import java.util.UUID;
public class NioServer {
public static void main(String[] args) throws Exception {
/**
* 开启一个服务端
* 设置为非阻塞
* 绑定端口号
*/
ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
serverSocketChannel.configureBlocking(false);
serverSocketChannel.bind(new InetSocketAddress(8080));
Selector selector = Selector.open();
serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
//UUID->客户端连接
Map clientMap = new HashMap<>();
while (true) {
selector.select();
Set selectionKeys = selector.selectedKeys();
selectionKeys.forEach(selectionKey -> {try {
if (selectionKey.isAcceptable()) {
/**
* 服务端接收到连接
* 保存接收到的客户端连接
*/
ServerSocketChannel server = (ServerSocketChannel) selectionKey.channel();
SocketChannel socketChannel = server.accept();
socketChannel.configureBlocking(false);
socketChannel.register(selector,SelectionKey.OP_READ);
String key = UUID.randomUUID().toString();
clientMap.put(key,socketChannel);
System.out.println(socketChannel.getRemoteAddress()+"连接上了服务器");
} else if (selectionKey.isReadable()) {
/**
* 读取客户端消息
* 转发到所有客户端
*/
SocketChannel socketChannel = (SocketChannel) selectionKey.channel();
try {
ByteBuffer buffer = ByteBuffer.allocate(1024);
int len = socketChannel.read(buffer);
if (len > 0) {
buffer.flip();
Charset charset = Charset.forName("UTF-8");
String receiveMsg = String.valueOf(charset.decode(buffer).array());
String key = null;
for (Map.Entry entry : clientMap.entrySet()) {
if (entry.getValue() == socketChannel) {
key = entry.getKey();
break;
}
}
String sendMsg = key + ":" + receiveMsg;
System.out.println(sendMsg);
for (Map.Entry entry : clientMap.entrySet()) {
ByteBuffer writeBuffer = ByteBuffer.allocate(1024);
writeBuffer.put(sendMsg.getBytes());
writeBuffer.flip();
entry.getValue().write(writeBuffer);
}
}
}catch (Exception e) {
e.printStackTrace();
//java.io.IOException: 远程主机强迫关闭了一个现有的连接。
socketChannel.close();
}
}
} catch (Exception e) {
e.printStackTrace();
}
});
selectionKeys.clear();
}}
}
客户端代码：
package com.imooc.nio;
import java.io.BufferedReader;
import java.io.InputStreamReader;
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.Set;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class NioClient {
public static void main(String[] args) throws Exception {
/**
* 开启一个客户端
* 设置为非阻塞
* 连接到服务器
*/
SocketChannel socketChannel = SocketChannel.open();
socketChannel.configureBlocking(false);
socketChannel.connect(new InetSocketAddress("localhost",8080));
Selector selector = Selector.open();
socketChannel.register(selector, SelectionKey.OP_CONNECT);
while (true) {
selector.select();
Set selectionKeys = selector.selectedKeys();
for (SelectionKey selectionKey : selectionKeys) {
if (selectionKey.isConnectable()) {
/**
* 客户端已连接
* 开启一个线程监听控制台输入
*/
SocketChannel client = (SocketChannel) selectionKey.channel();
if (client.isConnectionPending()) {
client.finishConnect();
}
client.register(selector,SelectionKey.OP_READ);
ExecutorService executor = Executors.newSingleThreadExecutor();
System.out.println(socketChannel.getLocalAddress()+"连上了服务器");
ByteBuffer writeBuffer = ByteBuffer.allocate(1024);
executor.submit(()->{
try {
while (true) {
writeBuffer.clear();
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
String line = reader.readLine();
writeBuffer.put(line.getBytes());
writeBuffer.flip();
client.write(writeBuffer);
}
}catch (Exception e) {
e.printStackTrace();
}
});
} else if (selectionKey.isReadable()) {
/**
* 打印服务端消息
*/
SocketChannel client = (SocketChannel) selectionKey.channel();
ByteBuffer readBuffer = ByteBuffer.allocate(1024);
int len = client.read(readBuffer);
System.out.println(new String(readBuffer.array(),0,len));
}
}
selectionKeys.clear();
}
}
}
【javaNIO的第一个例子】
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