Java Socket编程系列（四）开发支持多客户端访问的Server

例子来自Java官方教程，稍作调整。

上一篇介绍了单客户端访问的Server实现，这一篇实现的是多个客户端请求服务端，根据服务端提示进行一系列操作。

协议类（和系列三一样没变）：

package com.dylan.socket;/** * @author xusucheng * @create 2017-12-24 **/public class KnockKnockProtocol {    private static final int WAITING = 0;    private static final int SENTKNOCKKNOCK = 1;    private static final int SENTCLUE = 2;    private static final int ANOTHER = 3;    private static final int NUMJOKES = 5;    private int state = WAITING;    private int currentJoke = 0;    private String[] clues = { "Turnip", "Little Old Lady", "Atch", "Who", "Who" };    private String[] answers = { "Turnip the heat, it's cold in here!",            "I didn't know you could yodel!",            "Bless you!",            "Is there an owl in here?",            "Is there an echo in here?" };    public String processInput(String theInput) {        String theOutput = null;        if (state == WAITING) {            theOutput = "Knock! Knock!";            state = SENTKNOCKKNOCK;        } else if (state == SENTKNOCKKNOCK) {            if (theInput.equalsIgnoreCase("Who's there?")) {                theOutput = clues[currentJoke];                state = SENTCLUE;            } else {                theOutput = "You're supposed to say \"Who's there?\"! " +                        "Try again. Knock! Knock!";            }        } else if (state == SENTCLUE) {            if (theInput.equalsIgnoreCase(clues[currentJoke] + " who?")) {                theOutput = answers[currentJoke] + " Want another? (y/n)";                state = ANOTHER;            } else {                theOutput = "You're supposed to say \"" +                        clues[currentJoke] +                        " who?\"" +                        "! Try again. Knock! Knock!";                state = SENTKNOCKKNOCK;            }        } else if (state == ANOTHER) {            if (theInput.equalsIgnoreCase("y")) {                theOutput = "Knock! Knock!";                if (currentJoke == (NUMJOKES - 1))                    currentJoke = 0;                else                    currentJoke++;                state = SENTKNOCKKNOCK;            } else {                theOutput = "Bye.";                state = WAITING;            }        }        return theOutput;    }}

服务器端：

package com.dylan.socket;import java.io.IOException;import java.net.ServerSocket;/** * @author xusucheng * @create 2017-12-24 **/public class KKMultiServer {    private static final int PORT = 8858;    public static void main(String[] args) {        boolean listening = true;        try (ServerSocket serverSocket = new ServerSocket(PORT)) {            while (listening) {                new KKMultiServerThread(serverSocket.accept()).start();            }        } catch (IOException e) {            System.err.println("Could not listen on port " + PORT);            System.exit(-1);        }    }}

服务器多线程类（核心）：

package com.dylan.socket;import java.io.BufferedReader;import java.io.IOException;import java.io.InputStreamReader;import java.io.PrintWriter;import java.net.Socket;/** * @author xusucheng * @create 2017-12-24 **/public class KKMultiServerThread extends Thread{    private Socket socket = null;    public KKMultiServerThread(Socket socket) {        super("KKMultiServerThread");        this.socket = socket;    }    public void run() {        try (                PrintWriter out = new PrintWriter(socket.getOutputStream(), true);                BufferedReader in = new BufferedReader(                        new InputStreamReader(                                socket.getInputStream()));        ) {            String inputLine, outputLine;            KnockKnockProtocol kkp = new KnockKnockProtocol();            outputLine = kkp.processInput(null);            out.println(outputLine);            while ((inputLine = in.readLine()) != null) {                outputLine = kkp.processInput(inputLine);                out.println(outputLine);                if (outputLine.equals("Bye."))                    break;            }            socket.close();        } catch (IOException e) {            e.printStackTrace();        }    }}

客户端：

package com.dylan.socket;import java.io.BufferedReader;import java.io.IOException;import java.io.InputStreamReader;import java.io.PrintWriter;import java.net.Socket;import java.net.UnknownHostException;/** * @author xusucheng * @create 2017-12-24 **/public class KnockKnockClient {    private static final String HOST="127.0.0.1";    private static final int PORT=8858;    public static void main(String[] args) throws IOException {        /*if (args.length != 2) {            System.err.println(                    "Usage: java EchoClient <host name> <port number>");            System.exit(1);        }        String hostName = args[0];        int portNumber = Integer.parseInt(args[1]);*/        try (                Socket kkSocket = new Socket(HOST, PORT);                PrintWriter out = new PrintWriter(kkSocket.getOutputStream(), true);                BufferedReader in = new BufferedReader(                        new InputStreamReader(kkSocket.getInputStream()));        ) {            BufferedReader stdIn =                    new BufferedReader(new InputStreamReader(System.in));            String fromServer;            String fromUser;            while ((fromServer = in.readLine()) != null) {                System.out.println("Server: " + fromServer);                if (fromServer.equals("Bye."))                    break;                fromUser = stdIn.readLine();                if (fromUser != null) {                    System.out.println("Client: " + fromUser);                    out.println(fromUser);                }            }        } catch (UnknownHostException e) {            System.err.println("Don't know about host " + HOST);            System.exit(1);        } catch (IOException e) {            System.err.println("Couldn't get I/O for the connection to " +                    HOST);            System.exit(1);        }    }}