处理多线程与网络编程最为经典的例子莫过于聊天室，那我就聊天室案例作为一个回顾。
首先，我们来看以下代码：

package MultiTCP;import java.io.DataOutputStream;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket; /** * 必须先启动再连接 * 1、创建服务器 指定端口 ServerSocket(int port) * 2、接收客户端的连接 阻塞式 * 3、发送数据+接收数据 * * 接收多个客户端 */ @SuppressWarnings("all") public class MultiServer { public static void main(String[] args) throws IOException { //1、创建服务器 指定端口 ServerSocket server = new ServerSocket(8888); while(true)//死循环 一个accept 一个客户端 { //2、接收客户端的连接 Socket socket = server.accept(); System.out.println("一个客户端建立连接"); //2、发送数据 String msg = "欢迎使用"; //3、输出流 /*BufferedWriter bw = new BufferedWriter( new OutputStreamWriter( socket.getOutputStream())); bw.write(msg); bw.newLine();//一定要加行结束符，不然读不到数据 bw.flush();*/ DataOutputStream dos = new DataOutputStream(socket.getOutputStream()); dos.writeUTF(msg); dos.flush(); } } }

package MultiTCP;import java.io.DataInputStream;
import java.io.IOException;
import java.net.Socket;
import java.net.UnknownHostException; /** * 1、创建客户端 必须指定服务器+端口 此时就在连接 * Socket(String host,int port) * 2、接收数据+发送数据 */ @SuppressWarnings("all") public class Client { public static void main(String[] args) throws UnknownHostException, IOException { //1、创建客户端 必须指定服务器+端口 此时就在连接 Socket client = new Socket("localhost",8888); //2、接收数据 /*BufferedReader br = new BufferedReader(new InputStreamReader(client.getInputStream())); String echo = br.readLine();//阻塞式方法 System.out.println(echo);*/ DataInputStream dis = new DataInputStream(client.getInputStream()); String echo = dis.readUTF(); System.out.println(echo); } }

以上代码存在的问题
服务器为一个客户端发送数据完毕才能连接下一个客户端。
因此，为了解决上述的问题，我们需要为服务器端创建多线程操作。

首先我们需要为聊天室添加发送数据和接收数据。

package CSNet;import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.ServerSocket; import java.net.Socket; /** * 创建服务器 */ @SuppressWarnings("all") public class Server { public static void main(String[] args) throws IOException { ServerSocket server = new ServerSocket(9999); Socket client = server.accept(); //写出数据 //输入流 DataInputStream dis = new DataInputStream(client.getInputStream()); String msg = dis.readUTF(); System.out.println("服务器收到"+msg); //输出流 DataOutputStream dos = new DataOutputStream(client.getOutputStream()); dos.writeUTF("服务器发送给客户端"+msg); dos.flush(); } } 

package CSNet;import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException; import java.io.InputStreamReader; import java.net.Socket; import java.net.UnknownHostException; /** * 创建客户端：发送数据+接收数据 * 写出数据：输出流 * 读取数据：输入流 * 输入流与输出流在同一个线程内，因此我们应该让 输入流与输出流彼此独立 */ @SuppressWarnings("all") public class Client { public static void main(String[] args) throws UnknownHostException, IOException { Socket client = new Socket("localhost",9999); //控制台的输入流 BufferedReader console = new BufferedReader(new InputStreamReader(System.in)); DataOutputStream dos = new DataOutputStream(client.getOutputStream()); DataInputStream dis = new DataInputStream(client.getInputStream()); while(true) { String info = console.readLine(); //输出流 dos.writeUTF(info); dos.flush(); //输入流 String msg = dis.readUTF(); System.out.println(msg); } } }

以上的代码存在输入流与输出流在同一个线程内问题，因此我们应该让输入流与输出流彼此独立。

接下来我们是需要实现多线程，让输入流与输出流分离。对客户端实现多线程。

客户端发送数据

package ThreadNet;import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStreamReader; import java.net.Socket; /** * 发送数据线程：用于发送数据 */ public class Send implements Runnable{ //控制台的输入流 private BufferedReader console; //管道的数据输出流 private DataOutputStream dos; //控制线程标识 private boolean isRunning = true; //初始化 public Send() { console = new BufferedReader(new InputStreamReader(System.in)); } public Send(Socket client) { this(); try { dos = new DataOutputStream(client.getOutputStream()); } catch (IOException e) { } } //1、从控制台接收数据 private String getMsgFromConsole() { try { return console.readLine(); } catch (IOException e) { } return ""; } /** * 1、从控制台接收数据 * 2、发送数据 */ public void send() { String msg = getMsgFromConsole(); try { if(null!=msg&& !msg.equals("")) { dos.writeUTF(msg); dos.flush();//强制刷新 } } catch (IOException e) { isRunning = false;//发送失败，提示关闭线程 CloseUtil.closeAll(dos,console);//如果不能发送成功，直接关闭流。 } } @Override public void run() { //线程体 while(isRunning) { send(); } } } 

客户端接收数据

package ThreadNet;import java.io.DataInputStream;
import java.io.IOException;
import java.net.Socket;/** * 接收线程：用于接收数据 */ public class Receive implements Runnable{ //管道的数据输入流 private DataInputStream dis ; //线程标识 private boolean isRunning = true; public Receive() { } public Receive(Socket client) { try { dis = new DataInputStream(client.getInputStream()); } catch (IOException e) { isRunning = false; CloseUtil.closeAll(dis); } } //接收数据的方法 public String receive() { String msg = ""; try { msg = dis.readUTF(); } catch (IOException e) { isRunning = false; CloseUtil.closeAll(dis); } return msg; } @Override public void run() { //线程体 while(isRunning){ System.out.println(receive()); } } } 

客户端

package ThreadNet;import java.io.IOException;
import java.net.Socket;
import java.net.UnknownHostException;/** * 创建客户端：发送数据+接收数据 * 写出数据：输出流 * 读取数据：输入流 * 输入流与输出流在同一个线程内 应该独立出来 */ public class Client { public static void main(String[] args) throws UnknownHostException, IOException { Socket client = new Socket("localhost",9999); new Thread(new Send(client)).start();//一条路径 new Thread(new Receive(client)).start();//一条路径 } }

服务器

package ThreadNet;import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.ServerSocket; import java.net.Socket; /** * 创建服务器 */ public class Server { public static void main(String[] args) throws IOException { ServerSocket server = new ServerSocket(9999); while(true){ Socket client = server.accept(); //写出数据 //输入流 DataInputStream dis = new DataInputStream(client.getInputStream()); //输出流 DataOutputStream dos = new DataOutputStream(client.getOutputStream()); while(true) { String msg = dis.readUTF(); //System.out.println(msg); dos.writeUTF("服务器收到数据并返回"+msg); dos.flush(); } } } }

关闭流

package ThreadNet;import java.io.Closeable;
import java.io.IOException;/*** 关闭流的方法*/
public class CloseUtil { public static void closeAll(Closeable ... io) { for(Closeable temp:io) { if(null==temp) { try { temp.close(); } catch (IOException e) { e.printStackTrace(); } } } } }

这个方仍然存在问题，服务器端只能够一个一个的接收，必须要等到上一条执行完，才能进入下一条，存在所谓的先后顺序，并不具备多线程的功能。因此我们也需要对服务器进行多线程。

服务器

package MultiServer;import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.ServerSocket; import java.net.Socket; import java.util.ArrayList; import java.util.List; /** * 创建服务器 */ public class Server { private List<MyChannel> all = new ArrayList<>(); public static void main(String[] args) throws IOException { new Server().start(); } public void start() throws IOException { ServerSocket server = new ServerSocket(9999); while(true) { Socket client = server.accept(); MyChannel channel = new MyChannel(client); all.add(channel);//统一管理 new Thread(channel).start();//一条道路 } } /** * 内部类 * 一个客户端 一条道路 * 1、输入流 * 2、输出流 * 3、接收数据 * 4、发送数据 * @author Administrator * */ class MyChannel implements Runnable { private DataInputStream dis; private DataOutputStream dos; private boolean isRunning = true; private String name; public MyChannel() { } //初始化 public MyChannel(Socket client) { try { dis = new DataInputStream(client.getInputStream()); dos = new DataOutputStream(client.getOutputStream()); this.name = dis.readUTF(); //System.out.println(this.name); this.send("欢迎进入聊天室"); sendOthers(this.name+"进入了聊天室",true); } catch (IOException e) { CloseUtil.closeAll(dos,dis); isRunning = false; } } //接收数据 private String receive() { String msg = ""; try { msg = dis.readUTF(); } catch (IOException e) { CloseUtil.closeAll(dis); isRunning = false; all.remove(this);//移除自身 } return msg; } //发送数据 private void send(String msg) { if(null==msg||msg.equals("")) { return; } try { dos.writeUTF(msg); dos.flush(); } catch (IOException e) { CloseUtil.closeAll(dos); isRunning = false; all.remove(this);//移除自身 } } //发送给其他客户端 private void sendOthers(String msg,boolean sys) { //是否为私聊 约定 if(msg.startsWith("@")&& msg.indexOf(":")>-1) { //获取name String name = msg.substring(1,msg.indexOf(":")); String contant = msg.substring(msg.indexOf(":")+1); for(MyChannel other:all) { if(other.name.equals(name)) { other.send(this.name+"对你悄悄的说："+contant); } } } else { for(MyChannel other:all) { if(other ==this) { continue; } if(sys==true)//系统信息 { other.send("系统信息："+msg); } else { //发送其它客户端 other.send(this.name+"对所有人说"+msg); } } } /* //遍历容器 for(MyChannel others:all) { if(others == this) { continue; } //发送给其他客户端 others.send(msg); }*/ } @Override public void run() { while(isRunning) { sendOthers(receive(),false); } } } } 

发送信息（供客服端使用）

package MultiServer;import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStreamReader; import java.net.Socket; /** * 发送数据线程：用于发送数据 */ public class Send implements Runnable{ //控制台输入流 private BufferedReader console; //管道输出流 private DataOutputStream dos; //控制线程标识 private boolean isRunning = true; //名称 private String name; //初始化 public Send() { console = new BufferedReader(new InputStreamReader(System.in)); } public Send(Socket client,String name) { this(); try { dos = new DataOutputStream(client.getOutputStream()); this.name = name; send(this.name); } catch (IOException e) { //e.printStackTrace(); } } //1、从控制台接收数据 private String getMsgFromConsole() { try { return console.readLine(); } catch (IOException e) { e.printStackTrace(); } return ""; } /** * 1、从控制台接收数据 * 2、发送数据 */ public void send(String msg) { try { if(null!=msg&& !msg.equals("")) { dos.writeUTF(msg); dos.flush();//强制刷新 } } catch (IOException e) { //e.printStackTrace(); isRunning = false; CloseUtil.closeAll(dos,console); } } @Override public void run() { while(isRunning) { send( getMsgFromConsole()); } } }

接收信息（供客服端使用）

package MultiServer;import java.io.DataInputStream;
import java.io.IOException;
import java.net.Socket;/** * 接收线程：用于接收数据 */ public class Receive implements Runnable{ //管道的数据输入流 private DataInputStream dis ; //线程标识 private boolean isRunning = true; public Receive() { } public Receive(Socket client) { try { dis = new DataInputStream(client.getInputStream()); } catch (IOException e) { isRunning = false; CloseUtil.closeAll(dis); } } //接收数据的方法 public String receive() { String msg = ""; try { msg = dis.readUTF(); } catch (IOException e) { isRunning = false; CloseUtil.closeAll(dis); } return msg; } @Override public void run() { //线程体 while(isRunning){ System.out.println(receive()); } } } 

客户端

package MultiServer;import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.Socket; /** * 创建客户端：发送数据+接收数据 * 写出数据：输出流 * 读取数据：输入流 * 输入流与输出流在同一个线程内 应该独立出来 * 加入名称 */ public class Client { public static void main(String[] args) throws IOException { System.out.println("请输入用户名："); BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); String name = br.readLine(); if(name.equals("")) { return; } Socket client = new Socket("localhost",9999); new Thread(new Send(client,name)).start();//一条路径 new Thread(new Receive(client)).start();//一条路径 } }

关闭流

package MultiServer;import java.io.Closeable;
import java.io.IOException;/*** 关闭流的方法*/
public class CloseUtil { public static void closeAll(Closeable ... io) { for(Closeable temp:io) { if(null==temp) { try { temp.close(); } catch (IOException e) { e.printStackTrace(); } } } } } 

运行结果：
Client1

Client2