java网络编程——多线程数据收发并行

基本介绍与思路

收发并行

前一篇博客中，完成了客户端与服务端的简单TCP交互，但这种交互是触发式的：客户端发送一条消息，服务端收到后再回送一条。没有做到收发并行。收发并行的字面意思很容易理解，即数据的发送与接收互相不干扰，相互独立。当然，要保证服务端和客户端都能做到收发并行。

业务逻辑

脱离业务逻辑的实践是毫无意义的，先描述一下本实践中的业务逻辑：一个服务端接受多个客户端的连接，连接后，向各个客户端定时发送时间戳数据，同时在并行条件下，接受各个客户端发送来的数据并显示；客户端键盘输入字符串，发送给服务端，同时在并行条件下，接收服务器发来的时间戳数据并显示。

实现思路

实现发送与接收并行，思路其实非常直观，即建立两个线程，分别用来实现输入流和输出流。我的代码的设计方案如下图所示：

• 服务端：创建一个监听客户端连接的线程，线程中一旦接收到请求，创建一个对应该客户端收发处理的对象，对象中创建输入流线程，并使用单例线程池创建输出流线程。主线程使用键盘输入流System.in来进行阻塞。同时主线程中创建Timer定时器，定时向输出流发送数据。
• 客户端：主线程发送连接请求，与服务器建立连接。使用键盘输入流System.in来阻塞主线程，同时作为输出流使用；创建一个输入流线程，异步运行，接收服务器数据。

代码分析

源代码文件结构如下图所示

服务端

服务器端分为三个部分，分别是Server.java，TCPServer.java和ClientHandler.java

Server.java

package Server;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.text.SimpleDateFormat;
import java.util.TimerTask;
import java.util.Timer;
import java.util.Date;

public class Server {
    private static SimpleDateFormat df = new SimpleDateFormat("yyyyMMdd_HH:mm:ss");
    public static void main(String[] args){
        try {
            TCPServer.accept();
            new Timer("Timer").schedule(new TimerTask() {
                @Override
                public void run() {
                    TCPServer.broadcast(df.format(new Date()));
                }
            }, 1000,5000);
            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
            String str;
            //因为ClientListen是异步线程，使用键盘输入流将主线程阻塞住，保证跟ClientListen线程同步，同时可控制ClientListen服务的退出
            do{
                str = bufferedReader.readLine();
            }while (str.equalsIgnoreCase("serverExit"));
        }catch (Exception e){
            System.out.println("监听请求过程中异常退出");
        }

        try {
            TCPServer.stop();
        } catch (IOException e) {
            System.out.println("关闭套接字过程中出现异常");
        } finally {
            System.out.println("服务器端套接字已关闭！");
        }
    }

}

TCPServer.java

package Server;

import java.io.IOException;
import java.net.*;
import java.util.ArrayList;
import java.util.UUID;

class TCPServer {
    private static int LOCAL_PORT = 3001;
    private static ClientListenHandle clientListenHandle;
    private static ArrayList<ClientHandler> clientHandlerList = new ArrayList<ClientHandler>();

    static void accept() throws IOException {
        //创建服务器端套接字
        ServerSocket serverSocket = createSocket();
        InitSocket(serverSocket);
        System.out.println("服务器准备就绪 addr: " + Inet4Address.getLocalHost() + "  /port: " + LOCAL_PORT);
        System.out.println("开始监听客户端连接...");
        //创建线程监听客户端请求
        clientListenHandle = new ClientListenHandle(serverSocket);
        clientListenHandle.start();

    }

    static void stop() throws IOException {
        for (ClientHandler clientHandler : clientHandlerList) {
            clientHandler.socketClose();
        }
        clientHandlerList.clear();
        clientListenHandle.exit();
    }

    private static ServerSocket createSocket() throws IOException {
        ServerSocket socket = new ServerSocket(LOCAL_PORT, 50);
        return socket;
    }

    private static void InitSocket(ServerSocket socket) throws SocketException {
        // 是否复用未完全关闭的地址端口
        socket.setReuseAddress(true);

        // 等效Socket#setReceiveBufferSize
        socket.setReceiveBufferSize(64 * 1024 * 1024);

        // 设置serverSocket#accept超时时间，不设置即永久等待
        // serverSocket.setSoTimeout(2000);

        // 设置性能参数：短链接，延迟，带宽的相对重要性
        socket.setPerformancePreferences(1, 1, 1);
    }

    static void broadcast(String msg) {
        for (ClientHandler clientHandler : clientHandlerList) {
            clientHandler.write(msg);
        }

    }
    /**
     * 监听客户端请求的线程
     */
    static class ClientListenHandle extends Thread {
        private final ServerSocket serverSocket;
        private Boolean done = false;

        ClientListenHandle(ServerSocket serverSocket) {
            this.serverSocket = serverSocket;
        }

        @Override
        public void run() {
            super.run();
            try {
                do {
                    Socket client;
                    try {
                        client = serverSocket.accept();
                    } catch (Exception e) {
                        continue;//某一个客户端连接失败，要保证其它客户端能正常连接
                    }
                    String uuid = UUID.randomUUID().toString();//为客户端生成唯一标识
                    System.out.println("已接受连接client："+uuid+" /Addr:"+client.getInetAddress()+" /Port:"+client.getPort());
                    //为该客户端实例化一个ClientHandler对象，注入对象删除操作的lambda表达式
                    ClientHandler clientHandle = new ClientHandler(client, handler -> clientHandlerList.remove(handler), uuid);
                    clientHandle.read();
                    clientHandlerList.add(clientHandle);
                } while (!done);
            } catch (Exception e) {
                if (!done) {
                    System.out.println("异常退出！");
                }
            }
        }

        void exit() throws IOException {
            done = true;
            serverSocket.close();
        }
    }
}

ClientHandler.java

package Server;

import java.io.*;
import java.net.Socket;
import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class ClientHandler {
    private final Socket client;
    private final ReadHandler readHandler;
    private final WriteHandle writeHandler;
    private final Removable removable;
    private final String uid;

    ClientHandler(Socket socket, Removable removable, String uid) throws IOException {
        this.client = socket;
        this.readHandler = new ReadHandler(socket.getInputStream());
        this.writeHandler = new WriteHandle(socket.getOutputStream());
        this.removable = removable;
        this.uid = uid;
    }

    void read() {
        readHandler.start();
    }

    void write(String msg) {
        System.out.println("Server -->> " + uid + " : " + msg);
        writeHandler.write(msg);
    }

    /**
     * 把输入输出流和套接字都关闭
     */
    void socketClose(){
        try {
            readHandler.exit();
            writeHandler.exit();
            client.close();
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            System.out.println("客户端："+uid+" 套接字连接已关闭");
        }
    }
    /**
     * 把自身从对象列表中清除掉，具体方法是使用lambda表达式来注入的
     */
    void removeClientHandler() {
        removable.removeClientHandle(this);
    }

    /**
     * 定义一个接口，接收lambda表达式
     */
    interface Removable {
        void removeClientHandle(ClientHandler clientHandler);
    }

    /**
     * 输入流操作线程
     */
    class ReadHandler extends Thread {
        private final InputStream inputStream;
        private Boolean flag = true;

        ReadHandler(InputStream inputStream) {
            this.inputStream = inputStream;
        }

        @Override
        public void run() {
            super.run();

            BufferedReader socketInput = null;
            try {
                socketInput = new BufferedReader(new InputStreamReader(inputStream));
                do {

                    String str = socketInput.readLine();
                    //不知道为什么，客户端关闭时，这里直接报异常，获取不到null
                    if (str.equalsIgnoreCase("exit")) {
                        System.out.println("已无法读取客户端数据！");
                        throw new Exception();
                    }
                    System.out.println(uid + " -->> server : " + str);
                } while (flag);
            } catch (Exception e) {
                if (flag) {
                    System.out.println("读取客户端过程中异常退出");
                    ClientHandler.this.removeClientHandler();
                    ClientHandler.this.socketClose();
                }
            }
        }

        void exit() throws IOException {
            flag = false;
            inputStream.close();
        }
    }

    /**
     * 输出流操作线程，使用单例线程池，可以自动等待任务并处理，无需人工添加阻塞操作
     */
    class WriteHandle {
        private final OutputStream outputStream;
        private final ExecutorService executorService;

        WriteHandle(OutputStream outputStream) {
            this.outputStream = outputStream;
            this.executorService = Executors.newSingleThreadExecutor();
        }
        private void write(String msg){
            executorService.execute(new WriteRunnable(msg,outputStream));
        }
        void exit() throws IOException{
            outputStream.close();
            executorService.shutdown();
        }
        class WriteRunnable implements Runnable{
            private final String msg;
            private final PrintStream printStream;

            WriteRunnable(String msg, OutputStream outputStream) {
                this.msg = msg;
                this.printStream = new PrintStream(outputStream);
            }

            @Override
            public void run() {
                try {
                    printStream.println(msg);
                } catch (Exception e) {
                    System.out.println("打印输出异常！");
                }

            }
        }
    }
}

客户端

Client.java

package Client;

import java.io.*;
import java.util.UUID;

import Client.bean.ServerInfo;
public class Client {
    public static void main(String[] args)throws IOException {
        ServerInfo serverInfo = new ServerInfo(UUID.randomUUID().toString(),"127.0.2.16",3001);
        System.out.println("准备发起服务器连接...");
        System.out.println("服务器信息：Addr:"+serverInfo.getAddress()+" /Port:"+serverInfo.getPort());

        try {
            TCPClient.connect(serverInfo);
        }catch (Exception e){
            System.out.println("连接失败，退出");
        }
    }
}

TCPClient.java

package Client;

import Client.bean.ServerInfo;

import java.io.*;
import java.net.*;

class TCPClient {
    static void connect(ServerInfo serverInfo) throws IOException {
        Socket clientSocket = createSocket();//建立套接字

        InitSocket(clientSocket);//初始化套接字
        //连接远程服务器
        clientSocket.connect(new InetSocketAddress(serverInfo.getAddress(), serverInfo.getPort()), 3000);
        System.out.println("已连接server");
        try {
            //输入流线程
            ReadHandle readHandle = new ReadHandle(clientSocket.getInputStream());
            readHandle.start();

            //输出流
            write(clientSocket);
            //当输出流结束时，关闭输入流
            readHandle.exit();
        } catch (Exception e) {
            System.out.println("出现异常！");
        } finally {
            clientSocket.close();
            System.out.println("客户端结束");
        }
    }

    private static Socket createSocket() throws IOException {
        Socket socket = new Socket();
        return socket;
    }

    private static void InitSocket(Socket socket) throws SocketException {
        // 设置读取超时时间为2秒，超过2秒未获得数据时readline报超时异常；不设置即进行永久等待
        //socket.setSoTimeout(2000);
        // 是否复用未完全关闭的Socket地址，对于指定bind操作后的套接字有效
        socket.setReuseAddress(true);

        // 是否开启Nagle算法
        socket.setTcpNoDelay(true);

        // 是否需要在长时无数据响应时发送确认数据（类似心跳包），时间大约为2小时
        socket.setKeepAlive(true);

        // 对于close关闭操作行为进行怎样的处理；默认为false，0
        // false、0：默认情况，关闭时立即返回，底层系统接管输出流，将缓冲区内的数据发送完成
        // true、0：关闭时立即返回，缓冲区数据抛弃，直接发送RST结束命令到对方，并无需经过2MSL等待
        // true、200：关闭时最长阻塞200毫秒，随后按第二情况处理
        socket.setSoLinger(true, 20);

        // 是否让紧急数据内敛，默认false；紧急数据通过 socket.sendUrgentData(1);发送
        socket.setOOBInline(true);

        // 设置接收发送缓冲器大小
        socket.setReceiveBufferSize(64 * 1024 * 1024);
        socket.setSendBufferSize(64 * 1024 * 1024);

        // 设置性能参数：短链接，延迟，带宽的相对重要性
        socket.setPerformancePreferences(1, 1, 1);
    }

    /**
     * 输出流方法
     */
    private static void write(Socket socket) throws IOException {
        //构建键盘输入流
        InputStream in = System.in;
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(in));
        //得到socket输出流并转化为打印流
        OutputStream outputStream = socket.getOutputStream();
        PrintStream printStream = new PrintStream(outputStream);

        for(;;){
            String str = bufferedReader.readLine();//从键盘输入获取内容
            printStream.println(str);//通过打印流输出
            if(str.equalsIgnoreCase("exit")){
                break;
            }
        }

        printStream.close();
        System.out.println("输出流关闭");
    }


    /**
     * 输入流线程
     */
    static class ReadHandle extends Thread {
        private final InputStream inputStream;
        private Boolean done = false;

        ReadHandle(InputStream inputStream) {
            this.inputStream = inputStream;
        }

        @Override
        public void run() {
            super.run();
            try {
                //获取输入流
                BufferedReader socketInput = new BufferedReader(new InputStreamReader(inputStream));
                do {
                    String str;
                    str = socketInput.readLine();
                    if (str==null) {
                        break;
                    }
                    System.out.println("From server: "+ str);
                } while (!done);
            } catch (Exception e) {
                if (!done) {
                    System.out.println("异常断开，或者输入异常");
                }
            }
        }

        void exit() {
            done = true;
            try {
                inputStream.close();
            } catch (IOException e) {
                e.printStackTrace();
            }finally {
                System.out.println("输入流关闭");
            }
        }
    }
}

关于代码的具体分析，由于代码已有很多注释，博文中便不再赘述。

运行结果

运行结果如下所示

• 服务端
  
  连接成功后，服务端每隔5秒向各个客户端发送时间戳信息，同时接收两个客户端发来的信息

• 客户端1
  
  输入“I am client1”并向服务端发送，同时接收服务端发来的时间戳信息

• 客户端2
  
  输入“I am client2”并向服务端发送，同时接收服务端发来的时间戳信息

本篇博客记录一次实践学习，使用多线程+socket编程，实现了单服务器与多客户端之间的数据收发并行，除此之外，通过思维流程图，整理了代码的设计思路并展示出来。