Java - Use the MD5 checksum to confirm that the downloaded file is correct

本篇主旨在於client端下載server端的檔案後，進行MD5 checksum的檢查，確認檔案是否無誤!
程式撰寫如下:
1. 建立Server.java，等待Client端連線，連線上之後呈列目前可供下載的檔案
2. 建立Client.java，與Server端連線後，選擇檔案後進行下載
3. 建立Main.java，代表程式入口，可輸入相關參數選擇要執行哪一種模式(Server or Client)

#Server.java
  2. package service;
  3. import java.io.File;
  4. import java.io.FileInputStream;
  5. import java.io.IOException;
  6. import java.io.InputStream;
  7. import java.io.ObjectInputStream;
  8. import java.io.ObjectOutputStream;
  9. import java.net.ServerSocket;
  10. import java.net.Socket;
  12. import main.Main;
  14. public class Server {
  15. 	private ServerSocket server;
  16. 	private File sharePath;
  17. 	
  18. 	public Server(int port, File sharePath) throws IOException {
  19. 		this.sharePath = sharePath;
  20. 		this.server = new ServerSocket(port);
  21. 	}
  22. 	
  23. 	public void startService() {
  24. 		while(!server.isClosed()) {
  25. 		    try {
  26. 	               System.out.println("Waiting for the Client connection...");
  27. 	               Socket socket = server.accept();
  28. 	               String client = socket.getInetAddress().getHostAddress();
  29. 	               System.out.println("Connection received from: "+client);
  30. 	            
  31. 	               ObjectOutputStream oos = new ObjectOutputStream(socket.getOutputStream());
  32. 	               ObjectInputStream ois = new ObjectInputStream(socket.getInputStream());
  33. 	            
  34. 	               File listFiles[] = sharePath.listFiles();
  35. 	               oos.writeObject("The files that can be downloaded are as follows:");
  36. 	               int index = 0;
  37. 	               oos.writeObject(listFiles.length);
  38. 	               for(File f : listFiles) {
  39. 	                  oos.writeObject("("+(++index)+")"+f.getName());
  40. 	               }
  41. 	            
  42. 	               while (!socket.isClosed()) {
  43. 	                  System.out.println("Waiting for the "+client+" to send option id");
  44. 	            	  Object selection = ois.readObject();
  45. 	                
  46. 	                  if(selection instanceof Integer) {
  47. 	                     int sel = (int) selection;
  48. 	                     System.out.println("Client send option id is "+sel);
  49. 	                	
  50. 	                     if(sel == 0) {
  51. 	                        socket.close();
  52. 	                	break;
  53. 	                     }
  54. 	                     if(sel > listFiles.length) {
  55. 	                        System.out.println("File non-exist!!");
  56. 	                	oos.writeLong(-1L);
  57. 	                	oos.flush();
  58. 	                	continue;
  59. 	                     }
  60. 	                	
  61. 	                     File sendFile = listFiles[sel - 1];
  62. 	                     oos.writeLong(sendFile.length());
  63. 	                	
  64. 	                     oos.writeObject(sendFile.getName());
  65. 	                	
  66. 	                     String md5 = Main.getCheckSumByMD5(sendFile.getAbsolutePath());
  67. 	                     oos.writeObject(md5);
  68. 	                	
  69. 	                     InputStream is = new FileInputStream(sendFile);
  70.                 	     int read;
  71. 	                     byte[] buf = new byte[1024];
  72. 	                     while((read = is.read(buf, 0, buf.length)) != -1) {
  73. 	                        oos.write(buf, 0, read);
  74. 	                	oos.flush();
  75. 	                     }
  76. 	                	
  77. 	                     is.close();
  78. 	                     System.out.println("File "+sendFile.getName()+" transfer completed!");
  79. 	                     System.out.println("===========================");
  80. 	                  }
  81. 	               }
  82. 	               System.out.println("Client "+client+" disconnected!\n");
  83. 	               ois.close();
  84. 	               oos.close();
  85. 	            }catch (IOException | ClassNotFoundException e) {
  86. 	               e.printStackTrace();
  87. 	               terminateService();
  88. 	            }
  89. 		}
  90. 	}
  91. 	
  92. 	public void terminateService() {
  93. 		try {
  94. 	           this.server.close();
  95. 		   System.out.println("Shutdown server");
  96. 		} catch (IOException e) {
  97. 		   // TODO Auto-generated catch block
  98. 		   e.printStackTrace();
  99. 		}
  100. 	}
  101. }

client連上後，server傳送檔案清單，當收到項目的編號後，依序將檔案size(bytes)、名稱、md5 checksum傳給client，接下來就是data部分，buffer設定1024 bytes分批傳送! 傳送完畢後等待client下一個項目編號!
PS. 在這邊只示範傳送檔案，若是目錄不在測試範圍內

#Client.java
  2. package service;
  3. import java.io.File;
  4. import java.io.FileOutputStream;
  5. import java.io.IOException;
  6. import java.io.ObjectInputStream;
  7. import java.io.ObjectOutputStream;
  8. import java.net.InetAddress;
  9. import java.net.Socket;
  10. import java.net.UnknownHostException;
  11. import java.util.Scanner;
  13. import main.Main;
  15. public class Client {
  16. 	private File dPath;
  17. 	
  18. 	public Client(File downloadPath) {
  19. 		this.dPath = downloadPath;
  20. 	}
  21. 	
  22. 	public void startService() {
  23. 		InetAddress host;
  24. 		Scanner input = new Scanner(System.in);
  25. 		try {
  26. 		   host = InetAddress.getLocalHost();
  27. 		   Socket socket = new Socket(host.getHostName(), 5880);
  29. 		   ObjectOutputStream oos = new ObjectOutputStream(socket.getOutputStream());
  30.                    ObjectInputStream ois = new ObjectInputStream(socket.getInputStream());
  31.             
  32.                    System.out.println(ois.readObject());
  33.                    int num = (int) ois.readObject();
  34.                    int i = 0;
  35.                    while(i++ < num) {
  36.             	      System.out.println(ois.readObject());
  37.                    }
  38.             
  39.                    while(!socket.isClosed()) {
  40. 	              System.out.println("Waiting to send the option id [1 ~ "+num+"] to download file from server...");
  41. 	              System.out.println("Note. Terminate connection please input option 0");
  42. 	              int option = input.nextInt();
  43. 	            
  44. 	              oos.writeObject(option);
  45. 	              if(option == 0) {
  46. 	                 socket.close();
  47. 	            	 System.exit(-1);
  48. 	              }
  49. 	            
  50. 	              System.out.println("Send option id is "+option);
  51. 	            
  52. 	              long totalByte = ois.readLong();
  53. 	              if(totalByte == -1L) {
  54. 	                  System.out.println("Download file non-exist!!");
  55. 	            	  System.out.println("===========================");
  56. 	            	  continue;
  57. 	              }
  58. 	              System.out.println("Download file total size is "+totalByte+" bytes");
  59. 	            
  60. 	              String filename = (String) ois.readObject();
  61. 	              String checksum = (String) ois.readObject();
  62. 	            
  63. 	              String path = dPath.getAbsolutePath() + File.separator + filename;
  64. 	              System.out.println("Download to "+path);
  65. 	            
  66. 	              byte[] buffer = new byte[1024];
  67. 	              long cur = 0L;
  68. 	              FileOutputStream fos = new FileOutputStream(path);
  69. 	              while(cur < totalByte) {
  70. 	                 int len = ois.read(buffer);
  71. 	            	 cur += len;
  72. 	            	 fos.write(buffer, 0, len);
  73. 	            	 double percent = ((double)cur / totalByte) * 100;
  74. 	            	 System.out.println("Download current size = "+cur + " bytes, percent = "+percent+"%");
  75. 	              }
  76. 	              System.out.println("Download completed!!\n");
  77. 	              fos.close();
  78. 	        	
  79. 	              System.out.println("Check if the file is correct>>>");
  80. 	              String md5 = Main.getCheckSumByMD5(path);
  81. 	              System.out.println("Transferred file checksum => "+checksum);
  82. 	              System.out.println("Downloaded file checksum => "+md5);
  83. 	              if(md5.equals(checksum)) {
  84. 	                 System.out.println("Yes. It is corrent!");
  85. 	              }else {
  86. 	        	 System.out.println("No. It is incorrent!");
  87. 	              }
  88. 	              System.out.println("===========================");
  89.                    }
  90.                    input.close();
  91.                    ois.close();
  92.                    oos.close();
  93. 		} catch (UnknownHostException e) {
  94. 		   // TODO Auto-generated catch block
  95. 		   e.printStackTrace();
  96. 		} catch (IOException e) {
  97. 		   // TODO Auto-generated catch block
  98. 		   e.printStackTrace();
  99. 		} catch (ClassNotFoundException e) {
  100. 		   // TODO Auto-generated catch block
  101. 		   e.printStackTrace();
  102. 		}
  103. 	}
  104. }

client端連上server後，收到檔案清單，傳送項目編號後，收到檔案大小判斷是否存在，開始接收data後，計算當下下載進度，完畢後計算檔案md5 checksum，與server端的checksum進行比對，確認是否檔案傳輸正確!

#Main.java 
  2. package main;
  3. import java.io.File;
  4. import java.io.IOException;
  5. import java.io.InputStream;
  6. import java.nio.file.Files;
  7. import java.nio.file.Paths;
  9. import org.apache.commons.codec.digest.DigestUtils;
  11. import service.Client;
  12. import service.Server;
  14. public class Main {
  15. 	private static final int PORT = 5880;
  16. 	
  17. 	public static void main(String[] args) {
  18. 		// TODO Auto-generated method stub
  19. 		if(args.length == 0) {
  20. 			System.out.println("<<File Transfer Service>>"
  21. 					+ "\nStart client mode -> java -jar ftransfer.jar client [target path]"
  22. 					+ "\nStart server mode -> java -jar ftransfer.jar server [share path]");
  23. 		}else {
  24. 			if(args.length == 1) {
  25. 				System.out.println("Please specify path");
  26. 			}else {
  27. 				File path = new File(args[1]);
  28. 				if(!path.exists()) {
  29. 					System.out.println("The path non-exist");
  30. 				}else {
  31. 					String mode = args[0];
  32. 					if(mode.equals("server")) {
  33. 						Server server = null;
  34. 						try {
  35. 						    server = new Server(PORT, path);
  36. 						    server.startService();
  37. 						} catch (IOException e) {
  38. 						    // TODO Auto-generated catch block
  39. 						    e.printStackTrace();
  40. 						} finally {
  41. 						    if(server != null) {
  42. 						        server.terminateService();
  43. 						    }
  44. 						}
  45. 					}else if(mode.equals("client")) {
  46. 						Client client = new Client(path);
  47. 						client.startService();
  48. 					}
  49. 				}
  50. 			}
  51. 		}	
  52. 	}
  53. 	
  54. 	public static String getCheckSumByMD5(String filepath) throws IOException {
  55. 		try (InputStream is = Files.newInputStream(Paths.get(filepath))) {
  56. 		    return DigestUtils.md5Hex(is);
  57. 		}
  58. 	}
  60. }

依據主程式輸入的參數來決定開啟server or client mode

最後DEMO如下:
1. 透過eclipse輸出成可執行的jar檔FileTransfer.jar進行示範
2. 執行java -jar FileTransfer.jar (展現提示)
3. 啟動server，指定分享路徑D:\server
4. 啟動client，指定下載存放目錄E:\
5. server端輸出client端資訊，並且等待項目編號的回應
6. client端下載項目1
7. server端顯示收到需傳送項目1的檔案，傳送完畢後等待下一個項目要求
8. client端輸入無效id & terminate server connection
9. server端顯示檔案不存在 & terminate client connection
上面的步驟對照下面的圖示如下

留言

張貼留言