NIO系列：5.NIO群聊系统

NIO系列：5.NIO群聊系统

前面的文章介绍了NIO的三大核心组件并编写了BIO的一个demo实例，本文使用NIO写一个小应用实例，巩固并加深对NIO的理解。

实例要求：
1）编写一个 NIO 群聊系统，实现服务器端和客户端之间的数据简单通讯（非阻塞）
2）实现多人群聊
3）服务器端：可以监测用户上线，离线，并实现消息转发功能
4）客户端：通过channel 可以无阻塞发送消息给其它所有用户，同时可以接受其它用户发送的消息(有服务器转发得到)
5）目的：进一步理解NIO非阻塞网络编程机制

服务端代码：

import java.io.IOException;
import java.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.*;
import java.util.Iterator;public class GroupChatServer {//定义属性private Selector selector;private ServerSocketChannel listenChannel;private static final int PORT = 6667;//构造器//初始化工作public GroupChatServer() {try {//得到选择器selector = Selector.open();//ServerSocketChannellistenChannel =  ServerSocketChannel.open();//绑定端口listenChannel.socket().bind(new InetSocketAddress(PORT));//设置非阻塞模式figureBlocking(false);//将该listenChannel 注册到ister(selector, SelectionKey.OP_ACCEPT);}catch (IOException e) {e.printStackTrace();}}//监听public void listen() {System.out.println("监听线程: " + Thread.currentThread().getName());try {//循环处理while (true) {int count = selector.select();if(count > 0) {//有事件处理//遍历得到selectionKey 集合Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();while (iterator.hasNext()) {//取出selectionkeySelectionKey key = ();//监听到acceptif(key.isAcceptable()) {SocketChannel sc = listenChannel.accept();sc.configureBlocking(false);//将该 sc 注册到ister(selector, SelectionKey.OP_READ);//提示System.out.RemoteAddress() + " 上线 ");}if(key.isReadable()) { //通道发送read事件，即通道是可读的状态//处理读 (专门写方法..)readData(key);}//当前的key 删除，防止重复处理ve();}} else {System.out.println("等待....");}}}catch (Exception e) {e.printStackTrace();}finally {//发生异常处理....}}//读取客户端消息private void readData(SelectionKey key) {//取到关联的channleSocketChannel channel = null;try {//得到channelchannel = (SocketChannel) key.channel();//创建bufferByteBuffer buffer = ByteBuffer.allocate(1024);int count = ad(buffer);//根据count的值做处理if(count > 0) {//把缓存区的数据转成字符串String msg = new String(buffer.array());//输出该消息System.out.println("form 客户端: " + msg);//向其它的客户端转发消息(去掉自己), 专门写一个方法来处理sendInfoToOtherClients(msg, channel);}}catch (IOException e) {try {System.out.RemoteAddress() + " 离线了..");//取消注册key.cancel();//关闭通道channel.close();}catch (IOException e2) {e2.printStackTrace();;}}}//转发消息给其它客户(通道)private void sendInfoToOtherClients(String msg, SocketChannel self ) throws  IOException{System.out.println("服务器转发消息中...");System.out.println("服务器转发数据给客户端线程: " + Thread.currentThread().getName());//遍历 所有注册到selector 上的 SocketChannel,并排除 selffor(SelectionKey key: selector.keys()) {//通过 key  取出对应的 SocketChannelChannel targetChannel = key.channel();//排除自己if(targetChannel instanceof  SocketChannel && targetChannel != self) {//转型SocketChannel dest = (SocketChannel)targetChannel;//将msg 存储到bufferByteBuffer buffer = ByteBuffer.Bytes());//将buffer 的数据写入 通道dest.write(buffer);}}}public static void main(String[] args) {//创建服务器对象GroupChatServer groupChatServer = new GroupChatServer();groupChatServer.listen();}
}//可以写一个Handler
class MyHandler {public void readData() {}public void sendInfoToOtherClients(){}
}

客户端代码：

import java.io.IOException;
import java.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 GroupChatClient {//定义相关的属性private final String HOST = "127.0.0.1"; // 服务器的ipprivate final int PORT = 6667; //服务器端口private Selector selector;private SocketChannel socketChannel;private String username;//构造器, 完成初始化工作public GroupChatClient() throws IOException {selector = Selector.open();//连接服务器socketChannel = socketChannel.open(new InetSocketAddress("127.0.0.1", PORT));//设置非阻塞figureBlocking(false);//将channel 注册到ister(selector, SelectionKey.OP_READ);//得到usernameusername = LocalAddress().toString().substring(1);System.out.println(username + " ");}//向服务器发送消息public void sendInfo(String info) {info = username + " 说：" + info;try {socketChannel.write(ByteBuffer.Bytes()));}catch (IOException e) {e.printStackTrace();}}//读取从服务器端回复的消息public void readInfo() {try {int readChannels = selector.select();if(readChannels > 0) {//有可以用的通道Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();while (iterator.hasNext()) {SelectionKey key = ();if(key.isReadable()) {//得到相关的通道SocketChannel sc = (SocketChannel) key.channel();//得到一个BufferByteBuffer buffer = ByteBuffer.allocate(1024);//读取sc.read(buffer);//把读到的缓冲区的数据转成字符串String msg = new String(buffer.array());System.out.im());}}ve(); //删除当前的selectionKey, 防止重复操作} else {//System.out.println("没有可以用的通道...");}}catch (Exception e) {e.printStackTrace();}}public static void main(String[] args) throws Exception {//启动我们客户端GroupChatClient chatClient = new GroupChatClient();//启动一个线程, 每隔3秒，读取从服务器发送数据new Thread() {public void run() {while (true) {adInfo();try {Thread.currentThread().sleep(3000);}catch (InterruptedException e) {e.printStackTrace();}}}}.start();//发送数据给服务器端Scanner scanner = new Scanner(System.in);while (scanner.hasNextLine()) {String s = Line();chatClient.sendInfo(s);}}
}

注意：必须设置通道为非阻塞，才能向Selector注册，否则报 java.nio.channels.IllegalBlockingModeException 错
注意：在客户端上要想获取得到服务端的数据，也需要注册在register上(监听读事件)