说是简单聊天系统，压根不能算是一个系统，顶多算个雏形。本文重点不在聊天系统设计和实现上，而是通过实现类似效果，展示下NIO 和Socket两种编程方式的差异性。说是Socket与NIO的编程方式，不太严谨，因为NIO的底层也是通过Socket实现的，但又想不出非常好的题目，就这样吧。

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主要内容

Socket方式实现简易聊天效果

NIO方式实现简易聊天效果

两种方式的性能对比

前言

预期效果，是客户端之间进行“广播”式聊天，类似于QQ群聊天。希望以后有机会，以此简易版为基础，不断演进，演练下在线聊天系统。

1.Socket方式实现简易聊天效果

1.1服务端 Server.java

package com.example.socket.server;
import java.io.IOException;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
import java.util.List;
public class Server {
    private static int port =9999;
    // 可接受请求队列的最大长度
    private static int backlog=100;
    // 绑定到本机的IP地址
    private static final String bindAddr = "127.0.0.1";
    //socket字典列表
    private static List nodes= new ArrayList();
    public static void main(String[] args) {
        try {
            ServerSocket ss = new ServerSocket(port, backlog,InetAddress.getByName(bindAddr));
            for(;;){
                //发生阻塞,等待客户端连接            
                Socket sc = ss.accept();
                nodes.add(sc);
                InetAddress addr = sc.getLocalAddress();
                System.out.println("create new session from "+addr.getHostName()+":"+sc.getPort()+"\n");            
               //针对一个Socket 客户端 启动两个线程，分别是接收信息，发送信息
                new Thread(new ServerMessageReceiver(sc,nodes)).start();
                new ServerMessageSender(sc).start();
            }            
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

1.2 消息接收端 ServerMessageReceiver.java

额外负责信息广播

package com.example.socket.server;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.Socket;
import java.util.ArrayList;
import java.util.List;
/**
 * 
 * 接收消息
 *
 */
public class ServerMessageReceiver implements Runnable{
    private Socket socket;
    //socket字典列表
    private List nodes= new ArrayList();
    public ServerMessageReceiver(Socket sc,List nodes){
        this.socket=sc;
        this.nodes=nodes;
    }
    /**
     * 信息广播到其他节点
     */
    @Override
    public void run() {    
        try {
            BufferedReader reader = new BufferedReader(new InputStreamReader(socket.getInputStream(), "UTF-8"));
            //接收到的消息
            String content;
            while (true) {
                if(socket.isClosed()){
                    System.out.println("Socket已关闭，无法获取消息");
                    reader.close();
                    socket.close();
                    break;
                }
                content=reader.readLine();
                if(content!=null && content.equals("bye")){
                    System.out.println("对方请求关闭连接,无法继续进行聊天");
                    reader.close();
                    socket.close();
                    break;
                }
                String message =socket.getPort()+":"+content;
                //广播信息
                for(Socket n:this.nodes){
                    if(n !=this.socket){
                        BufferedWriter writer=new BufferedWriter(new OutputStreamWriter(n.getOutputStream(),"UTF-8"));
                        writer.write(message);
                        writer.newLine();
                        writer.flush();        
                    }
                }
            }
        } catch (IOException e) {            
            e.printStackTrace();
        }
        
    }

}

1.3消息发送服务端 ServerMessageSender.java

主要作用：发送欢迎信息

package com.example.socket.server;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.net.Socket;
public class ServerMessageSender extends Thread{
    private Socket socket;

    public ServerMessageSender(Socket socket) {
        this.socket = socket;
    }
/**
 * 只发送一个欢迎信息
 */
    @Override
    public void run() {
        try {
            BufferedWriter writer=new BufferedWriter(new OutputStreamWriter(socket.getOutputStream(),"UTF-8"));
//            BufferedReader inputReader=new BufferedReader(new InputStreamReader(System.in));
            try {
                String msg="server :welcome "+socket.getPort();
                writer.write(msg);
                writer.newLine();
                writer.flush();
            } catch (IOException e) {
                e.printStackTrace();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

1.4 客户端 Client.java

package com.example.socket.client;
import java.net.InetAddress;
import java.net.Socket;

public class Client {
    // 监听端口号
    private static final int port = 9999;
    // 绑定到本机的IP地址
    private static final String bindAddr = "127.0.0.1";

    public static void main(String[] args) {
        try {
            System.out.println("正在连接Socket服务器");
            Socket socket=new Socket(InetAddress.getByName(bindAddr),port);
            System.out.println("已连接\n==================================");
            new ClientMessageSender(socket).start();
            new ClientMessageReceiver(socket).start();
        } catch (Exception e) {
            e.printStackTrace();
        }
        
    }
}

1.4 消息接收客户端  ClientMessageReceiver.java

仅仅是输出

package com.example.socket.client;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.Socket;

public class ClientMessageReceiver extends Thread {
    
    private Socket socket;
    
    public ClientMessageReceiver(Socket socket) {
        this.socket=socket;    
    }

    @Override
    public void run() {
        try {
            // 获取socket的输 出\入流
            BufferedReader reader = new BufferedReader(new InputStreamReader(socket.getInputStream(), "UTF-8"));
            //接收到的消息
            String content;
            while (true) {
                if(socket.isClosed()){
                    System.out.println("Socket已关闭，无法获取消息");
                    reader.close();
                    socket.close();
                    break;
                }
                content=reader.readLine();
                if(content.equals("bye")){
                    System.out.println("对方请求关闭连接,无法继续进行聊天");
                    reader.close();
                    socket.close();
                    break;
                }
                System.out.println(content+"\n");
            }
            reader.close();
            socket.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    
}

1.5 消息发送客户端 ClientMessageSender.java

通过输入流输入，将信息传入Socket

package com.example.socket.client;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.Socket;

public class ClientMessageSender extends Thread {
    
    private Socket socket;

    public ClientMessageSender(Socket socket) {
        this.socket = socket;
    }

    @Override
    public void run() {
        try {
            BufferedWriter writer=new BufferedWriter(new OutputStreamWriter(socket.getOutputStream(),"UTF-8"));
            BufferedReader inputReader=new BufferedReader(new InputStreamReader(System.in));
            try {
                String msg;
                for(;;){
                    msg=inputReader.readLine();
                    if(msg.toLowerCase().equals("exit")){
                        System.exit(0);
                    }
                    if(socket.isClosed()){
                        System.out.println("Socket已关闭，无法发送消息");
                        writer.close();
                        socket.close();
                        break;
                    }
                    writer.write(msg);
                    writer.newLine();
                    writer.flush();
                    System.out.println();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    
}

1.6 效果

2.NIO方式实现简易聊天效果

2.1服务端 NServer.java

package com.example.nio;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.Channel;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.nio.charset.Charset;

/**
 * 服务器端
 */
public class NServer {
    private Selector selector;
    private Charset charset = Charset.forName("UTF-8");
    
    public void init() throws Exception {
        selector = Selector.open();
        ServerSocketChannel server = ServerSocketChannel.open();
        InetSocketAddress isa = new InetSocketAddress("127.0.0.1", 3000);
        server.socket().bind(isa);
        server.configureBlocking(false);
        server.register(selector, SelectionKey.OP_ACCEPT);
        while (selector.select() > 0) {
            for (SelectionKey key : selector.selectedKeys()) {
                selector.selectedKeys().remove(key);
                if (key.isAcceptable()) {
                    SocketChannel sc = server.accept();
                    System.out.println("create new session from "+sc.getRemoteAddress()+"\n");
                    sc.configureBlocking(false);
                    sc.register(selector, SelectionKey.OP_READ);
                    key.interestOps(SelectionKey.OP_ACCEPT);        
                    sc.write(charset.encode("welcome"+sc.getRemoteAddress()));
                }
                
                if (key.isReadable()) {
                    SocketChannel sc = (SocketChannel)key.channel();
                    ByteBuffer buff = ByteBuffer.allocate(1024);
                    String content = "";
                    try {
                        while (sc.read(buff) > 0) {
                            buff.flip();
                            content += charset.decode(buff);
                            buff.clear();
                        }                        
                        key.interestOps(SelectionKey.OP_READ);
                    } catch (IOException e) {
                        key.cancel();
                        if (key.channel() != null)
                            key.channel().close();
                    }
                    if (content.length() > 0) {
                        for (SelectionKey sk : selector.keys()) {
                            Channel targetchannel = sk.channel();
                           if (targetchannel instanceof SocketChannel && targetchannel!=sc) {
                                SocketChannel dest = (SocketChannel)targetchannel;
                                dest.write(charset.encode(content));
                            }
                        }
                    }
                }
            }
        }
    }
    
    public static void main(String[] args) throws Exception {
        new NServer().init();
    }
}

2.2 客户端 NClient.java

package com.example.nio;
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.nio.charset.Charset;
import java.util.Scanner;

/**
 * 客户端
 */
public class NClient {
    private Selector selector;
    private Charset charset = Charset.forName("UTF-8");
    private SocketChannel sc = null;
    
    public void init() throws IOException {
        selector = Selector.open();
        InetSocketAddress isa = new InetSocketAddress("127.0.0.1", 3000);
        sc = SocketChannel.open(isa);
        sc.configureBlocking(false);
        sc.register(selector, SelectionKey.OP_READ);
        new ClientThread().start();
        @SuppressWarnings("resource")
        Scanner scan = new Scanner(System.in);
        while (scan.hasNextLine()) {
            sc.write(charset.encode(scan.nextLine()));
        }
    }
    
    private class ClientThread extends Thread {
        public void run() {
            try {
                while (selector.select() > 0) {
                    for (SelectionKey sk : selector.selectedKeys()) {
                        selector.selectedKeys().remove(sk);
                        if (sk.isReadable()) {
                            SocketChannel sc = (SocketChannel)sk.channel();
                            ByteBuffer buff = ByteBuffer.allocate(1024);
                            String content = "";
                            while (sc.read(buff) > 0) {
                                sc.read(buff);
                                buff.flip();
                                content += charset.decode(buff);
                                buff.clear();
                            }
                            System.out.println("chat info: " + content);
                            sk.interestOps(SelectionKey.OP_READ);
                        }
                    }
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
    
    public static void main(String[] args) throws IOException {
        new NClient().init();
    }
}

代码来自

https://github.com/xeostream/chat
2.3 效果

3. 对比

从API操作上来看，NIO偏复杂，面向的是异步编程方式，重点围绕Selector，SelectKey操作。

性能对比，主要简单模拟下Echo情景：客户端连接成功，服务端返回一条信息。

3.1Socket性能测试入口

可以关闭ServerMessageReceiver线程

package com.example.socket.client;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;

public class BenchmarkClient {
    // 监听端口号
    private static final int port = 9999;
    // 绑定到本机的IP地址
    private static final String bindAddr = "127.0.0.1";

    /**
     * @param 
     * @param args
     */
    public static  void main(String[] args) {
        try {
            long s=System.currentTimeMillis();
            for (int i = 0; i < 1000; i++) {
                final Socket socket = new Socket(
                        InetAddress.getByName(bindAddr), port);
                Future future = Executors.newFixedThreadPool(4).submit(
                        new Callable() {
                            @Override
                            public String call() throws Exception {
                                BufferedReader reader = new BufferedReader(
                                        new InputStreamReader(socket
                                                .getInputStream(), "UTF-8"));
                                String content = reader.readLine();
                                return Thread.currentThread().getName()+"--->"+content;
                            }
                        });                
                System.out.println(i+":"+future.get());
                socket.close();
            }
            long e=System.currentTimeMillis();
            System.out.println(e-s);
        } catch (UnknownHostException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (ExecutionException e) {
            e.printStackTrace();
        }

    }

}

3.2 NIO性能测试入口

package com.example.nio;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
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.nio.charset.Charset;
import java.util.Scanner;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;

/**
 * 客户端
 * @author arthur
 */
public class BenchMarkNClient {
    private Selector selector;
    private Charset charset = Charset.forName("UTF-8");
    private SocketChannel sc = null;
    
    public void init() throws IOException {
        long s = System.currentTimeMillis();
        selector = Selector.open();
        InetSocketAddress isa = new InetSocketAddress("127.0.0.1", 3000);
        for (int i = 0; i < 10000; i++) {    
            sc = SocketChannel.open(isa);
            sc.configureBlocking(false);
            sc.register(selector, SelectionKey.OP_READ);
            Future future = Executors.newFixedThreadPool(4).submit(new ClientTask());
            try {
                System.out.println(i+":"+future.get());
            } catch (InterruptedException e) { 
                e.printStackTrace();
            } catch (ExecutionException e) {
                e.printStackTrace();
            }
        }
        long e= System.currentTimeMillis();
        System.out.println(e-s);
    }
    
    private class ClientTask implements Callable {
        public String call() {
            try {
                while (selector.select() > 0) {
                    for (SelectionKey sk : selector.selectedKeys()) {
                        selector.selectedKeys().remove(sk);
                        if (sk.isReadable()) {
                            SocketChannel sc = (SocketChannel)sk.channel();
                            ByteBuffer buff = ByteBuffer.allocate(1024);
                            String content = "";
                            while (sc.read(buff) > 0) {
                                sc.read(buff);
                                buff.flip();
                                content += charset.decode(buff);
                                buff.clear();
                            }

                            sk.interestOps(SelectionKey.OP_READ);
                            return content;
                        }
                    }
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
            return null;
        }
    }
    
    public static void main(String[] args) throws IOException {
        new BenchMarkNClient().init();
    }
}

3.3 性能对比

次数	NIO	SOCKET（ms）
1000	525	637
2000	1411	1215
2000（休眠时间为100毫秒）	205928	206313
5000	6731	2976

次数较少时，NIO性能较好。但随着次数增加，性能下降非常厉害。（存疑）

当通讯时间变长时，发现NIO性能又相对提高了。

可见一个技术的好坏，是和业务场景分不开的。

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