20165225 實驗五 網絡編程與安全

實驗報告封面:

課程：Java程序設計  班級：1652班  姓名：王高源 學號：20165225

指導教師：婁嘉鵬 實驗日期：2018年5月14日

實驗時間：3：35 - 5：15 實驗序號：實驗5

實驗名稱：網絡編程與安全

實驗內容：

1、掌握Java Socket的相關內容；
2、學會建立客戶端與服務器端之間的聯系；
3、學習並應用密碼學的相關內容

嚴禁抄襲，有該行為者實驗成績歸零，並附加其他懲罰措施。

網絡編程與安全一：

實驗要求：

兩人一組結對編程：

參考http://www.cnblogs.com/rocedu/p/6766748.html#SECDSA
結對實現中綴表達式轉後綴表達式的功能 MyBC.java
結對實現從上面功能中獲取的表達式中實現後綴表達式求值的功能,調用MyDC.java

實驗代碼：

Client

import java.net.*;
import java.io.*;
public class Client
{
    public static void main(String srgs[]) throws Exception
    {
        try
        {
            // 1、創建客戶端Socket，指定服務器地址和端口
            Socket socket=new Socket("127.0.0.1",10000);
            System.out.println("客戶端成功啟動，等待服務器應答");
            // 2、獲取輸出流，向服務器端發送信息
            // 向本機的10001端口發出客戶請求
            System.out.println("請輸入中綴表達式：");
            BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
            // 由系統標準輸入設備構造BufferedReader對象
            PrintWriter write = new PrintWriter(socket.getOutputStream());
            // 由Socket對象得到輸出流，並構造PrintWriter對象
            //3、獲取輸入流，並讀取服務器端的響應信息
            BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            // 由Socket對象得到輸入流，並構造相應的BufferedReader對象
            String readline, infix, expression;
            readline = br.readLine(); // 從系統標準輸入讀入一字符串
            MyBC theTrans = new MyBC(readline);
            infix = theTrans.doTrans();
            StringBuilder newInfix = new StringBuilder(infix.replace(" ",""));
            for (int i = 1; i < infix.length()+(i+1)/2 ; i=i+2) {
                newInfix.insert(i," ");
            }
            System.out.println("後綴表達式：" + newInfix);
            expression=newInfix.toString();

            while (!readline.equals("end")) {
                // 若從標準輸入讀入的字符串為 "end"則停止循環
                write.println(expression);
                // 將從系統標準輸入讀入的字符串輸出到Server
                write.flush();
                // 刷新輸出流，使Server馬上收到該字符串
                System.out.println("收到服務器的消息:" + in.readLine());
                // 從Server讀入一字符串，並打印到標準輸出上
                readline = br.readLine(); // 從系統標準輸入讀入一字符串
            } // 繼續循環
            //4、關閉資源
            write.close(); // 關閉Socket輸出流
            in.close(); // 關閉Socket輸入流
            socket.close(); // 關閉Socket
        }
        catch (Exception e)
        {
            System.out.println(e);//輸出異常
        }
        finally
        {

        }

    }
}
 

Server

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

public class Server{
    public static void main(String srgs[]) throws Exception
    {
        ServerSocket sc = null;
        Socket socket=null;
        try
        {
            MyDC evaluator = new MyDC();

            sc= new ServerSocket(10000);//創建服務器套接字
            System.out.println("端口號:" + sc.getLocalPort());
            System.out.println("服務器成功啟動，等待客戶端呼叫");
            socket = sc.accept();   //等待客戶端連接
            System.out.println("已經建立連接");//獲得網絡輸入流對象的引用
            BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));//獲得網絡輸出流對象的引用
            PrintWriter out=new PrintWriter(new BufferedWriter(new OutputStreamWriter(socket.getOutputStream())),true);
            String aline2=in.readLine();
            System.out.println("客戶端發來的信息為："+aline2);

            int ans = evaluator.evaluate(aline2);
            out.println(ans);
            System.out.println("result = "+ans);
        } catch (Exception e) {
            System.out.println(e);
        }
    }

    //十六進制和十進制轉換
    public static byte[] parseHexStr2Byte(String hexStr)
    {
        if (hexStr.length() < 1)
            return null;
        byte[] result = new byte[hexStr.length()/2];
        for (int i = 0;i< hexStr.length()/2; i++)
        {
            int high = Integer.parseInt(hexStr.substring(i*2, i*2+1 ), 16);
            int low = Integer.parseInt(hexStr.substring(i*2+1, i*2+2), 16);
            result[i] = (byte) (high * 16 + low);
        }
        return result;
    }
}
 

MyDc

import java.util.StringTokenizer;
import java.util.Stack;

public class MyDC {
    /**
     * constant for addition symbol
     */
    private final char ADD = ‘+‘;
    /**
     * constant for subtraction symbol
     */
    private final char SUBTRACT = ‘-‘;
    /**
     * constant for multiplication symbol
     */
    private final char MULTIPLY = ‘*‘;
    /**
     * constant for division symbol
     */
    private final char DIVIDE = ‘/‘;
    /**
     * the stack
     */
    private Stack<Integer> stack;

    public MyDC() {
        stack = new Stack<Integer>();
    }

    public int evaluate(String expr) {
        int op1, op2, result = 0;
        String token;
        StringTokenizer tokenizer = new StringTokenizer(expr);
        while (tokenizer.hasMoreTokens()) {
            token = tokenizer.nextToken();

            //如果是運算符，調用isOperator
            if (isOperator(token)) {
                //從棧中彈出操作數2
                op2 = stack.pop();
                //從棧中彈出操作數1
                op1 = stack.pop();
                //根據運算符和兩個操作數調用evalSingleOp計算result;
                result=evalSingleOp(token.charAt(0), op1, op2);
                //計算result入棧;
                stack.push(result);
            } else//如果是操作數
                //操作數入棧;
                stack.push(Integer.parseInt(token));
        }

        return result;
    }

    private boolean isOperator(String token) {
        return (token.equals("+") || token.equals("-") ||
                token.equals("*") || token.equals("/"));
    }

    private int evalSingleOp(char operation, int op1, int op2) {
        int result = 0;

        switch (operation) {
            case ADD:
                result = op1 + op2;
                break;
            case SUBTRACT:
                result = op1 - op2;
                break;
            case MULTIPLY:
                result = op1 * op2;
                break;
            case DIVIDE:
                result = op1 / op2;
        }

        return result;
    }
}

MyBc

public class MyBC {
    private Stack theStack;
    private String input;
    private String output = "";
    public MyBC(String in) {
        input = in;
        int stackSize = input.length();
        theStack = new Stack(stackSize);
    }
    public String doTrans() {
        for (int j = 0; j < input.length(); j++) {
            char ch = input.charAt(j);
            switch (ch) {
                case ‘+‘:
                case ‘-‘:
                    gotOper(ch, 1);
                    break;
                case ‘*‘:
                case ‘/‘:
                    gotOper(ch, 2);
                    break;
                case ‘(‘:
                    theStack.push(ch);
                    break;
                case ‘)‘:
                    gotParen(ch);
                    break;
                default:
                    output = output + ch;
                    break;
            }
        }
        while (!theStack.isEmpty()) {
            output = output + theStack.pop();
        }
        return output;
    }
    public void gotOper(char opThis, int prec1) {
        while (!theStack.isEmpty()) {
            char opTop = theStack.pop();
            if (opTop == ‘(‘) {
                theStack.push(opTop);
                break;
            }
            else {
                int prec2;
                if (opTop == ‘+‘ || opTop == ‘-‘)
                    prec2 = 1;
                else
                    prec2 = 2;
                if (prec2 < prec1) {
                    theStack.push(opTop);
                    break;
                }
                else
                    output = output + opTop;
            }
        }
        theStack.push(opThis);
    }
    public void gotParen(char ch){
        while (!theStack.isEmpty()) {
            char chx = theStack.pop();
            if (chx == ‘(‘)
                break;
            else
                output = output + chx;
        }
    }
    class Stack {
        private int maxSize;
        private char[] stackArray;
        private int top;
        public Stack(int max) {
            maxSize = max;
            stackArray = new char[maxSize];
            top = -1;
        }
        public void push(char j) {
            stackArray[++top] = j;
        }
        public char pop() {
            return stackArray[top--];
        }
        public char peek() {
            return stackArray[top];
        }
        public boolean isEmpty() {
            return (top == -1);
        }
    }
}

實驗截圖：

網絡編程與安全二：

結對編程：1人負責客戶端，一人負責服務器

註意責任歸宿，要會通過測試證明自己沒有問題
基於Java Socket實現客戶端/服務器功能，傳輸方式用TCP
客戶端讓用戶輸入中綴表達式，然後把中綴表達式調用MyBC.java的功能轉化為後綴表達式，把後綴表達式通過網絡發送給服務器
服務器接收到後綴表達式，調用MyDC.java的功能計算後綴表達式的值，把結果發送給客戶端
客戶端顯示服務器發送過來的結果

實驗代碼：

Server

import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
public class Server1 {
    public static void main(String args[]) {
        ServerSocket serverForClient = null;
        Socket socketOnServer = null;
        DataOutputStream out = null;
        DataInputStream in = null;
        try {
            serverForClient = new ServerSocket(3001);
        } catch (IOException e1) {
            System.out.println(e1);
        }
        try {
            System.out.println("等待客戶呼叫");
            socketOnServer = serverForClient.accept(); //堵塞狀態，除非有客戶呼叫
            System.out.println("客戶已連接");
            out = new DataOutputStream(socketOnServer.getOutputStream());
            in = new DataInputStream(socketOnServer.getInputStream());
            String leng = in.readUTF(); // in讀取信息，堵塞狀態
            byte ctext[] = new byte[Integer.parseInt(leng)];
            for (int i = 0;i<Integer.parseInt(leng);i++) {
                String temp = in.readUTF();
                ctext[i] = Byte.parseByte(temp);
            }
            // 獲取密鑰
            FileInputStream f2 = new FileInputStream("keykb1.txt");
            int num2 = f2.available();
            byte[] keykb = new byte[num2];
            f2.read(keykb);
            SecretKeySpec k = new SecretKeySpec(keykb, "DESede");
            // 解密
            Cipher cp = Cipher.getInstance("DESede");
            cp.init(Cipher.DECRYPT_MODE, k);
            byte[] ptext = cp.doFinal(ctext);
            System.out.println("後綴表達式已被解密：");
            for (int i = 0; i < ptext.length; i++) {
                System.out.print(ptext[i] + ",");
            }
            System.out.println("");
            // 顯示明文
            String p = new String(ptext, "UTF8");
            System.out.println("服務器收到客戶的請求:計算後綴表達式" + p);
            MyDC evaluator = new MyDC();
            out.writeUTF(evaluator.evaluate(p)+"");
        } catch (Exception e) {
            System.out.println("客戶已斷開" + e);
        }
    }
}

Client

實驗截圖：

網絡編程與安全三：

加密結對編程：1人負責客戶端，一人負責服務器

註意責任歸宿，要會通過測試證明自己沒有問題
基於Java Socket實現客戶端/服務器功能，傳輸方式用TCP
客戶端讓用戶輸入中綴表達式，然後把中綴表達式調用MyBC.java的功能轉化為後綴表達式，把後綴表達式用3DES或AES算法加密後通過網絡把密文發送給服務器
服務器接收到後綴表達式表達式後，進行解密（和客戶端協商密鑰，可以用數組保存），然後調用MyDC.java的功能計算後綴表達式的值，把結果發送給客戶端
客戶端顯示服務器發送過來的結果

實驗代碼：

Server

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
import java.security.Key;
import java.util.Optional;

public class Server2 {
    public static void main(String args[]) {
        ServerSocket serverForClient = null;
        Socket socketOnServer = null;
        DataOutputStream out = null;
        DataInputStream in = null;
        try {
            serverForClient = new ServerSocket(2010);
        } catch (IOException e1) {
            System.out.println(e1);
        }
        try {
            System.out.println("等待客戶呼叫");
            socketOnServer = serverForClient.accept(); //堵塞狀態，除非有客戶呼叫
            System.out.println("客戶已連接");
            out = new DataOutputStream(socketOnServer.getOutputStream());
            in = new DataInputStream(socketOnServer.getInputStream());

            Key_DH.fun("Spub.txt","Spri.txt");
            int len = Integer.parseInt(in.readUTF());
            byte np[] = new byte[len];
            for (int i = 0;i<len;i++) {
                String temp = in.readUTF();
                np[i] = Byte.parseByte(temp);
            }
            ObjectInputStream ois = new ObjectInputStream (new ByteArrayInputStream (np));
            Key k2 = (Key)ois.readObject();;
            FileOutputStream f2 = new FileOutputStream("Cpub.txt");
            ObjectOutputStream b2 = new ObjectOutputStream(f2);
            b2.writeObject(k2);

            FileInputStream fp = new FileInputStream("Spub.txt");
            ObjectInputStream bp = new ObjectInputStream(fp);
            Key kp = (Key) bp.readObject();
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            ObjectOutputStream oos = new ObjectOutputStream(baos);
            oos.writeObject(kp);
            byte[] kb = baos.toByteArray();
            out.writeUTF(kb.length + "");
            for (int i = 0; i < kb.length; i++) {
                out.writeUTF(kb[i] + "");
            }

            KeyAgree.fun("Cpub.txt","Spri.txt");

            String leng = in.readUTF(); // in讀取信息，堵塞狀態
            byte ctext[] = new byte[Integer.parseInt(leng)];
            for (int i = 0;i<Integer.parseInt(leng);i++) {
                String temp = in.readUTF();
                ctext[i] = Byte.parseByte(temp);
            }
            // 獲取密鑰
            FileInputStream f = new FileInputStream("sb.txt");
            byte[] keysb = new byte[24];
            f.read(keysb);
            System.out.println("公共密鑰：");
            for (int i = 0;i<24;i++) {
                System.out.print(keysb[i]+",");
            }
            System.out.println("");
            SecretKeySpec k = new SecretKeySpec(keysb, "DESede");
            // 解密
            Cipher cp = Cipher.getInstance("DESede");
            cp.init(Cipher.DECRYPT_MODE, k);
            byte[] ptext = cp.doFinal(ctext);
            System.out.println("後綴表達式已被解密：");
            for (int i = 0; i < ptext.length; i++) {
                System.out.print(ptext[i] + ",");
            }
            System.out.println("");
            // 顯示明文
            String p = new String(ptext, "UTF8");
            System.out.println("服務器收到客戶的請求:計算後綴表達式" + p);
            MyDC evaluator = new MyDC();
            out.writeUTF(evaluator.evaluate(p)+"");
        } catch (Exception e) {
            System.out.println("客戶已斷開" + e);
        }
    }
}

實驗編程：

網絡編程與安全四：

密鑰分發結對編程：1人負責客戶端，一人負責服務器

註意責任歸宿，要會通過測試證明自己沒有問題
基於Java Socket實現客戶端/服務器功能，傳輸方式用TCP
客戶端讓用戶輸入中綴表達式，然後把中綴表達式調用MyBC.java的功能轉化為後綴表達式，把後綴表達式用3DES或AES算法加密通過網絡把密文發送給服務器
客戶端和服務器用DH算法進行3DES或AES算法的密鑰交換
服務器接收到後綴表達式表達式後，進行解密，然後調用MyDC.java的功能計算後綴表達式的值，把結果發送給客戶端
客戶端顯示服務器發送過來的結果

實驗代碼：

server

import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
import java.security.Key;

public class Server3 {
    public static void main(String args[]) {
        ServerSocket serverForClient = null;
        Socket socketOnServer = null;
        DataOutputStream out = null;
        DataInputStream in = null;
        try {
            serverForClient = new ServerSocket(3001);
        } catch (IOException e1) {
            System.out.println(e1);
        }
        try {
            System.out.println("等待客戶呼叫");
            socketOnServer = serverForClient.accept(); //堵塞狀態，除非有客戶呼叫
            System.out.println("客戶已連接");
            out = new DataOutputStream(socketOnServer.getOutputStream());
            in = new DataInputStream(socketOnServer.getInputStream());

            Key_DH.fun("Spub.txt","Spri.txt");
            int len = Integer.parseInt(in.readUTF());
            byte np[] = new byte[len];
            for (int i = 0;i<len;i++) {
                String temp = in.readUTF();
                np[i] = Byte.parseByte(temp);
            }
            ObjectInputStream ois = new ObjectInputStream (new ByteArrayInputStream(np));
            Key k2 = (Key)ois.readObject();;
            FileOutputStream f2 = new FileOutputStream("Cpub.txt");
            ObjectOutputStream b2 = new ObjectOutputStream(f2);
            b2.writeObject(k2);

            FileInputStream fp = new FileInputStream("Spub.txt");
            ObjectInputStream bp = new ObjectInputStream(fp);
            Key kp = (Key) bp.readObject();
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            ObjectOutputStream oos = new ObjectOutputStream(baos);
            oos.writeObject(kp);
            byte[] kb = baos.toByteArray();
            out.writeUTF(kb.length + "");
            for (int i = 0; i < kb.length; i++) {
                out.writeUTF(kb[i] + "");
            }

            KeyAgree.fun("Cpub.txt","Spri.txt");

            String leng = in.readUTF(); // in讀取信息，堵塞狀態
            byte ctext[] = new byte[Integer.parseInt(leng)];
            for (int i = 0;i<Integer.parseInt(leng);i++) {
                String temp = in.readUTF();
                ctext[i] = Byte.parseByte(temp);
            }
            String check = in.readUTF();
            // 獲取密鑰
            FileInputStream f = new FileInputStream("sb.txt");
            byte[] keysb = new byte[24];
            f.read(keysb);
            System.out.println("公共密鑰：");
            for (int i = 0;i<24;i++) {
                System.out.print(keysb[i]+",");
            }
            System.out.println("");
            SecretKeySpec k = new SecretKeySpec(keysb, "DESede");
            // 解密
            Cipher cp = Cipher.getInstance("DESede");
            cp.init(Cipher.DECRYPT_MODE, k);
            byte[] ptext = cp.doFinal(ctext);
            System.out.println("後綴表達式已被解密：");
            for (int i = 0; i < ptext.length; i++) {
                System.out.print(ptext[i] + ",");
            }
            System.out.println("");
            // 顯示明文
            String p = new String(ptext, "UTF8");
            String pMd5 = DigestPass.fun(p);
            System.out.println("解密後明文的MD5值："+pMd5);
            if (pMd5.equals(check)){
                System.out.println("和客戶端的MD5值一致");
                System.out.println("服務器收到客戶的請求:計算後綴表達式" + p);
                MyDC evaluator = new MyDC();
                out.writeUTF(evaluator.evaluate(p)+"");
            }
            else {
                System.out.println("警告：和客戶端的MD5值不一致！");
            }
        } catch (Exception e) {
            System.out.println("客戶已斷開" + e);
        }
    }
}

實驗截圖：

網絡編程與安全五：

完整性校驗結對編程：1人負責客戶端，一人負責服務器

註意責任歸宿，要會通過測試證明自己沒有問題
基於Java Socket實現客戶端/服務器功能，傳輸方式用TCP
客戶端讓用戶輸入中綴表達式，然後把中綴表達式調用MyBC.java的功能轉化為後綴表達式，把後綴表達式用3DES或AES算法加密通過網絡把密文和明文的MD5値發送給服務器
客戶端和服務器用DH算法進行3DES或AES算法的密鑰交換
服務器接收到後綴表達式表達式後，進行解密，解密後計算明文的MD5值，和客戶端傳來的MD5進行比較，一致則調用MyDC.java的功能計算後綴表達式的值，把結果發送給客戶端
客戶端顯示服務器發送過來的結果

實驗代碼：

Client

import java.net.*;
import java.io.*;
public class Client
{
    public static void main(String srgs[]) throws Exception
    {
        try
        {
            // 1、創建客戶端Socket，指定服務器地址和端口
            Socket socket=new Socket("127.0.0.1",10000);
            System.out.println("客戶端成功啟動，等待服務器應答");
            // 2、獲取輸出流，向服務器端發送信息
            // 向本機的10001端口發出客戶請求
            System.out.println("請輸入中綴表達式：");
            BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
            // 由系統標準輸入設備構造BufferedReader對象
            PrintWriter write = new PrintWriter(socket.getOutputStream());
            // 由Socket對象得到輸出流，並構造PrintWriter對象
            //3、獲取輸入流，並讀取服務器端的響應信息
            BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            // 由Socket對象得到輸入流，並構造相應的BufferedReader對象
            String readline, infix, expression;
            readline = br.readLine(); // 從系統標準輸入讀入一字符串
            MyBC theTrans = new MyBC(readline);
            infix = theTrans.doTrans();
            StringBuilder newInfix = new StringBuilder(infix.replace(" ",""));
            for (int i = 1; i < infix.length()+(i+1)/2 ; i=i+2) {
                newInfix.insert(i," ");
            }
            System.out.println("後綴表達式：" + newInfix);
            expression=newInfix.toString();

            while (!readline.equals("end")) {
                // 若從標準輸入讀入的字符串為 "end"則停止循環
                write.println(expression);
                // 將從系統標準輸入讀入的字符串輸出到Server
                write.flush();
                // 刷新輸出流，使Server馬上收到該字符串
                System.out.println("收到服務器的消息:" + in.readLine());
                // 從Server讀入一字符串，並打印到標準輸出上
                readline = br.readLine(); // 從系統標準輸入讀入一字符串
            } // 繼續循環
            //4、關閉資源
            write.close(); // 關閉Socket輸出流
            in.close(); // 關閉Socket輸入流
            socket.close(); // 關閉Socket
        }
        catch (Exception e)
        {
            System.out.println(e);//輸出異常
        }
        finally
        {

        }

    }
}import java.net.*;
import java.io.*;
public class Client
{
    public static void main(String srgs[]) throws Exception
    {
        try
        {
            // 1、創建客戶端Socket，指定服務器地址和端口
            Socket socket=new Socket("127.0.0.1",10000);
            System.out.println("客戶端成功啟動，等待服務器應答");
            // 2、獲取輸出流，向服務器端發送信息
            // 向本機的10001端口發出客戶請求
            System.out.println("請輸入中綴表達式：");
            BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
            // 由系統標準輸入設備構造BufferedReader對象
            PrintWriter write = new PrintWriter(socket.getOutputStream());
            // 由Socket對象得到輸出流，並構造PrintWriter對象
            //3、獲取輸入流，並讀取服務器端的響應信息
            BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            // 由Socket對象得到輸入流，並構造相應的BufferedReader對象
            String readline, infix, expression;
            readline = br.readLine(); // 從系統標準輸入讀入一字符串
            MyBC theTrans = new MyBC(readline);
            infix = theTrans.doTrans();
            StringBuilder newInfix = new StringBuilder(infix.replace(" ",""));
            for (int i = 1; i < infix.length()+(i+1)/2 ; i=i+2) {
                newInfix.insert(i," ");
            }
            System.out.println("後綴表達式：" + newInfix);
            expression=newInfix.toString();

            while (!readline.equals("end")) {
                // 若從標準輸入讀入的字符串為 "end"則停止循環
                write.println(expression);
                // 將從系統標準輸入讀入的字符串輸出到Server
                write.flush();
                // 刷新輸出流，使Server馬上收到該字符串
                System.out.println("收到服務器的消息:" + in.readLine());
                // 從Server讀入一字符串，並打印到標準輸出上
                readline = br.readLine(); // 從系統標準輸入讀入一字符串
            } // 繼續循環
            //4、關閉資源
            write.close(); // 關閉Socket輸出流
            in.close(); // 關閉Socket輸入流
            socket.close(); // 關閉Socket
        }
        catch (Exception e)
        {
            System.out.println(e);//輸出異常
        }
        finally
        {

        }

    }
}

實驗截圖：

PSP(Personal Software Process)時間：

實驗五 網絡編程與安全