今天给同事写了一个socket bio的demo让他来测试用，顺便分享给大家，希望可以帮助正在学习和了解java bio的新人们

java.net.socket 是java中最基本的socket bio实现方式。

本例实现了多人互动广播

Server端

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.BindException;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.SocketException;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;/*** * @author Allen 2017年7月19日**/
public class SocketServer {/*** class constant*/static int POST = 44554;static String NOTE_FORMAT_INFO = "[%s:%s]<ID:%s> %s %s \n";static ExecutorService threads;static PrintWriter pw = null;static Map<Integer, Socket> alls = new HashMap<Integer, Socket>();//保存ClientSocket的容器,可以进行统计,定向广播等public static void main(String[] args) throws IOException {//初始化指定大小的线程池threads = Executors.newFixedThreadPool(Runtime.getRuntime().availableProcessors() << 3);SocketServer socketServer = new SocketServer();try {socketServer.openServer();} catch (BindException e) {System.out.printf("%s [%s] %s", "端口", POST, "被占用");}}public void openServer() throws BindException, IOException {ServerSocket server = null;int uid = 0;try {server = new ServerSocket(POST);System.out.println("服务器启动成功");while (true) {//为什么while(true)因为要不断的保证进入下面的阻塞来接收新的客户端//SocketServer通过阻塞来获取一个new Socket//java如何实现的accept阻塞？通过源码最终指向下面方法//当看到native我们就不需要在去考虑了//native是什么？native是调用本地方法//static native int accept0(int fd, InetSocketAddress[] isaa) throws IOException;Socket socket = server.accept();//当用户连接成功时我们给他发送一条欢迎消息sendHelp("连接成功 --  From SocketServer", null, socket); //通过线程池启动线程并把我们uid+1,当然这里的uid没有原子性//原子性怎么做？synchronized/CAS/AtomicInteger皆可threads.execute(new ClientSocekt(socket, ++uid));}} finally {if (server != null && !server.isClosed())server.close();}}private void sendHelp(String msg, Socket nowSocket, Socket... sockets) throws IOException {if (sockets == null || sockets.length == 0)//把alls的值通过toArray(T[] t)转成Socket[]sockets = alls.values().toArray(new Socket[0]);for (Socket s : sockets) {//把消息广播到sockets[]pw = new PrintWriter(s.getOutputStream());//如果不是println就一定要在后面加上"\n"pw.println(nowSocket != null && s.hashCode() == nowSocket.hashCode() ? "send success" : msg);pw.flush();}}class ClientSocekt extends Thread {Socket socket;Integer uid;BufferedReader br;public ClientSocekt(Socket socket, Integer uid) {this.socket = socket;alls.put(uid, socket);this.uid = uid;}@Overridepublic void run() {try {//通过bufferedReader从缓冲区读取数据br = new BufferedReader(new InputStreamReader(socket.getInputStream()));String line = null;//readline也是阻塞的//本demo没有把粘包等问题考虑//如果想解决粘包最简单的就是用read，创建一个Byte//用byte去接,byte设定一个大小//传输的文本改用 {Length|Context|Type|End} 这种方式//当得到length > byte.length的时候继续去缓冲区获取数据，知道此数据获取完毕while ((line = br.readLine()) != null) {System.out.printf(NOTE_FORMAT_INFO, socket.getInetAddress().toString(), socket.getPort(), uid,"收到: ", line);sendHelp("来自: "+socket.getInetAddress().toString()+":"+socket.getPort()+"的消息: "+line, socket);}} catch (SocketException e) {System.out.printf(NOTE_FORMAT_INFO, socket.getInetAddress().toString(), socket.getPort(), uid, "状态: ","离开了");} catch (Exception e) {e.printStackTrace();} finally {alls.remove(uid);clear();}}private void clear() {if (br != null)try {br.close();} catch (IOException e) {e.printStackTrace();}if (socket != null)try {socket.close();} catch (IOException e) {e.printStackTrace();}//销毁客户端线程this.interrupt();}}
}

Client端

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.SocketException;
import java.util.Scanner;public class SocketClient { // 搭建客户端/*** class constant*/static int POST = 44554;static String IP = "127.0.0.1";public static void main(String[] args) throws IOException {SocketClient socketClient = new SocketClient();try {socketClient.openClient();} catch (Exception e) {e.printStackTrace();System.out.println("连接失败");}}@SuppressWarnings("resource")public void openClient() throws IOException {Socket socket = new Socket(IP, POST);//连接成功后我们就建一个阻塞的IO来获取server广播的消息new ReadMsg(socket).start();System.out.println("客户端启动成功");PrintWriter pw = null;while (true) {//通过Scanner阻塞的接收键盘输入的信息发送到serverpw = new PrintWriter(socket.getOutputStream());pw.println(new Scanner(System.in).next());pw.flush();}}/*** 监听收到的消息* * @author Allen 2017年7月19日**/class ReadMsg extends Thread {Socket socket;BufferedReader br;public ReadMsg(Socket socket) {this.socket = socket;}@Overridepublic void run() {try {br = new BufferedReader(new InputStreamReader(socket.getInputStream()));String line = null;while (true) {while ((line = br.readLine()) != null)System.out.printf("%s\n",line);}} catch (SocketException e) {System.out.printf("%s\n","服务器断开了你的连接");} catch (Exception e) {e.printStackTrace();} finally {clear();}}private void clear() {if (br != null)try {br.close();} catch (IOException e1) {e1.printStackTrace();}if (socket != null)try {socket.close();} catch (IOException e) {e.printStackTrace();}this.interrupt();}}
}

输出

服务器启动成功
[/172.26.106.38:53305]<ID:1> 收到:  我是Allen 
[/172.26.106.38:53307]<ID:2> 收到:  我是赵钱孙 
[/172.26.106.47:50359]<ID:3> 收到:  RRRR 

客户端启动成功
连接成功 --  From SocketServer
我是Allen
send success
来自: /172.26.106.38:53307的消息: 我是赵钱孙
来自: /172.26.106.47:50359的消息: RRRR

客户端启动成功
连接成功 --  From SocketServer
来自: /172.26.106.38:53305的消息: 我是Allen
我是赵钱孙
send success
来自: /172.26.106.47:50359的消息: RRRR

是不是很简单，没什么复杂的，把线程和容器搞明白了，阻塞IO还有数据传输搞懂了，基本就可以了