1.BIO 

客户端简单编写

public static void main(String[] args) {try {//1.创建socket对象Socket socket=new Socket("127.0.0.1", 9999);//2.从socket 获取字节输入流OutputStream out=socket.getOutputStream();//字节输入流换成打印流PrintStream ps=new PrintStream(out,true);Scanner san=new Scanner(System.in);while (true){System.out.print("请说：");ps.println(san.nextLine()) ;}} catch (IOException e) {e.printStackTrace();}}

服务端简单编写

public static void main(String[] args) {try {System.out.println("开始注册端口");//注册端口ServerSocket serversocket=new ServerSocket(9999);//循环获取socket 监听while(true){Socket so=serversocket.accept();new ServerThread(so).start();}} catch (Exception e) {e.printStackTrace();}
}

定义一个ServerThread线程类

public class ServerThread extends Thread{private Socket socket;public ServerThread(Socket so) {this.socket=so;}@Overridepublic void run() {try {InputStream input=socket.getInputStream();BufferedReader read=new BufferedReader(new InputStreamReader(input));String msg;while( (msg=read.readLine())!=null ){System.out.println(msg);}} catch (Exception e) {e.printStackTrace();}}
}

2. NIO 代码开发，同样也是实现客户端和服务端交互

客户端：

public class Client {//1.选择器private Selector selector;//2.客户端通道private SocketChannel socketChannel;//3.端口private static int PORT = 9998;//4.IPprivate static String IP="127.0.0.1";//5.实例化public Client(){try {//6.开启选择器selector=Selector.open();//7.开启通道socketChannel=SocketChannel.open(new InetSocketAddress(IP,PORT));//8.设置非阻塞socketChannel.configureBlocking(false);//9.绑定端口IP//  socketChannel.bind(new InetSocketAddress(IP,PORT));//10 监听读事件socketChannel.register(selector, SelectionKey.OP_READ);System.out.println("客户端准备好了");} catch (IOException e) {System.out.println("客户端连接失败");e.printStackTrace();}}public static void main(String[] args) {Client client=new Client();System.out.println("转发线程启动");new Thread(() -> {System.out.println("开始转发");client.readInfo();}).start();Scanner sc=new Scanner(System.in);while (sc.hasNext()){String msg=  sc.nextLine();client.writrToServer(msg);System.out.println("-------------");}}private void writrToServer(String msg) {try {socketChannel.write(ByteBuffer.wrap(msg.getBytes()));} catch (IOException e) {e.printStackTrace();}}private void readInfo() {try {while(selector.select()>0) {Iterator<SelectionKey> it =selector.selectedKeys().iterator();while(it.hasNext()){//取数SelectionKey sk=it.next();if(sk.isReadable()){SocketChannel sc= (SocketChannel) sk.channel();ByteBuffer bf=ByteBuffer.allocate(1024);sc.read(bf);bf.flip();System.out.println(new String(bf.array(),0,bf.remaining()));System.out.println("----转发结束---------");}it.remove();}}} catch (IOException e) {e.printStackTrace();}}}

服务端：

public class Server {//1.private ServerSocketChannel sschannel;//2.private Selector selector;//3.定义端口private final int PORT=9998;//构造器public Server(){try {//开启选择器,初始化选择器selector=Selector.open();//开启通道sschannel=ServerSocketChannel.open();//设置非阻塞sschannel.configureBlocking(false);//设置连接sschannel.bind(new InetSocketAddress(PORT));//注册连接事件sschannel.register(selector, SelectionKey.OP_ACCEPT);} catch (IOException e) {e.printStackTrace();}}public void connect() {try {System.out.println("服务端准备就绪");//有连接的事件就一直循环等待while (selector.select()>0){//迭代所有事件Iterator<SelectionKey> it=selector.selectedKeys().iterator();while (it.hasNext()){//获取当前事件SelectionKey sk= it.next();//判断事件状态if(sk.isAcceptable()){//11.获取当前接入客户端通道SocketChannel sc= sschannel.accept();//设置事件通道阻塞sc.configureBlocking(false);//13.本客户端注册读事件到选择器sc.register(selector,SelectionKey.OP_READ);}else if(sk.isReadable()){clientGetData(sk);}it.remove();}}}catch (Exception e){}}private void clientGetData(SelectionKey sk) {//获取当前事件通道SocketChannel socketChannel= null;//分配空间ByteBuffer bf=ByteBuffer.allocate(1024);try {socketChannel= (SocketChannel) sk.channel();int leg=socketChannel.read(bf);if(leg>0){bf.flip();String msg=new String(bf.array(),0,bf.remaining());System.out.println("客户端接收消息："+msg);sendMsgAllclient(msg,socketChannel);}} catch (IOException e) {System.out.println("有人离线了");try {sk.cancel();socketChannel.close();} catch (IOException ioException) {ioException.printStackTrace();}e.printStackTrace();}}private void sendMsgAllclient(String msg, SocketChannel socketChannel) {System.out.println("服务端开始转发这个消息，当前线程："+Thread.currentThread().getName());for(SelectionKey skey : selector.keys()){Channel channel=  skey.channel();if(channel instanceof SocketChannel && channel!=socketChannel){ByteBuffer buffer=ByteBuffer.wrap(msg.getBytes());try {((SocketChannel) channel).write(buffer);} catch (IOException e) {System.out.println("为啥没有收到");e.printStackTrace();}}}}public static void main(String[] args) {Server server=new Server();server.connect();}}