实例要求：
- 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）
- 实现多人群聊
- 服务器端：可以监测用户上线，离线，并实现消息转发功能
- 客户端：通过channel可以无阻塞发送消息给其他所有用户，同时可以接受其它用户发送的消息（由服务器转发得到）
服务器端代码实现
package com.example.demo.netty.groupchat;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.*;
import java.util.Iterator;
public class GroupChatServer {
//自定义属性
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();
//serverSocketChannel
listenChannel = ServerSocketChannel.open();
//绑定端口
listenChannel.bind(new InetSocketAddress(PORT));
//设置非阻塞模式
listenChannel.configureBlocking(false);
//将该listenChannel注册到selector
listenChannel.register(selector, SelectionKey.OP_ACCEPT);
} catch (IOException e) {
e.printStackTrace();
}
}
//监听
public void listen() {
try {
while (true) {
int count = selector.select(2000);
if ( count > 0) { //有事件处理
Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();
while (iterator.hasNext()) {
SelectionKey key = iterator.next();
//监听到accept
if (key.isAcceptable()) {
SocketChannel sc = listenChannel.accept();
//设置非阻塞模式
sc.configureBlocking(false);
// 将该 sc 注册到 selector
sc.register(selector, SelectionKey.OP_READ);
//提示
System.out.println(sc.getRemoteAddress() + " 上线 ");
}
// 通道发送read事件，即通道是可读的状态
if (key.isReadable()) {
readData(key);
}
// 当前的key 删除，防止重复处理
iterator.remove();
}
} else {
System.out.println("等待.....");
}
}
} catch (IOException e) {
e.printStackTrace();
}
}
//读取客户端消息
public void readData(SelectionKey key) {
// 取到客户端关联的channel
SocketChannel channel = null;
try {
channel = (SocketChannel)key.channel();
ByteBuffer byteBuffer = ByteBuffer.allocate(1024);
int count = channel.read(byteBuffer);
if (count > 0) {
String msg = new String(byteBuffer.array());
System.out.println("from 客户端:" + msg);
// 向其他的客户端转发消息（去掉自己），专门写一个方法来处理
sendInfoToOtherClients(msg, channel);
}
} catch (IOException e) {
try {
System.out.println(channel.getRemoteAddress() + " 离线了... ");
//取消注册
key.cancel();
//关闭通道
channel.close();
} catch (IOException e2) {
e2.printStackTrace();
}
}
}
//转发消息给其他客户（通道）
public void sendInfoToOtherClients(String msg, SocketChannel self) throws IOException {
System.out.println("服务器转发消息中...");
//遍历 所有注册到selector上的 socketChannel，并排除 self
for (SelectionKey key : selector.keys()) {
// 通过 key 取出对应的 socketChannel
Channel targetChannel = key.channel();
// 排除自己
if (targetChannel instanceof SocketChannel && targetChannel != self) {
//转型
SocketChannel dest = (SocketChannel)targetChannel;
//将msg 存储到buffer
ByteBuffer buffer = ByteBuffer.wrap(msg.getBytes());
//将buffer的数据写入通道
dest.write(buffer);
}
}
}
public static void main(String[] args) {
GroupChatServer groupChatServer = new GroupChatServer();
groupChatServer.listen();
}
}
客户端代码实现
package com.example.demo.netty.groupchat;
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;
public class GroupChatClient {
//定义相关的属性
private final String HOST = "127.0.0.1"; //服务器ip
private 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(HOST, PORT));
//设置非阻塞
socketChannel.configureBlocking(false);
//将 channel注册到 selector
socketChannel.register(selector, SelectionKey.OP_READ);
//得到username
username = socketChannel.getLocalAddress().toString().substring(1);
System.out.println(username + " is ok....");
}
//向服务器发送消息
public void sendInfo(String info) {
info = username + " 说：" + info;
try {
socketChannel.write(ByteBuffer.wrap(info.getBytes()));
} 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) {//有可用的通道
Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();
while (iterator.hasNext()) {
SelectionKey key = iterator.next();
if (key.isReadable()) {
//得到相关的通道
SocketChannel sc = (SocketChannel) key.channel();
//得到一个buffer
ByteBuffer buffer = ByteBuffer.allocate(1024);
//读取
sc.read(buffer);
//把读到的缓冲区的数据转换成字符串
String msg = new String(buffer.array());
System.out.println(msg.trim());
}
iterator.remove();// 删除当前的selectionKey，防止重复处理
}
}
} catch (IOException e) {
e.printStackTrace();
}
}
public static void main(String[] args) throws Exception {
GroupChatClient chatClient = new GroupChatClient();
new Thread() {
public void run () {
while(true){
chatClient.readInfo();
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 = scanner.nextLine();
chatClient.sendInfo(s);
}
}
}
