獲取ConnectionException：在文件傳輸應用程序上拒絕連接

Question

因此，我創建了一個簡單的文件傳輸應用程序。當我運行它時，我得到一個Connection refused錯誤。現在，防火牆沒有問題，因爲當我嘗試從我正在遵循的書中運行示例代碼時，它運行得很完美。服務器啓動時沒有錯誤。

Server代碼：

public class Server 
{ 
final static int TRANSFER_PORT = 1215; 
final static int FILEINFO_PORT = 1216; 
static int filesize; 
static String filename; 

public static void main(String[] args) throws IOException 
{ 
    ServerSocket fileInfoSocket = new ServerSocket(FILEINFO_PORT); 
    try 
    { 
     System.out.println("Server Started"); 
     Socket s = fileInfoSocket.accept(); 
     System.out.println("Connected"); 
     InputStream is = s.getInputStream(); 
     DataInputStream dis = new DataInputStream(is); 
     filesize = dis.readInt(); 
     filename = dis.readUTF(); 
     s.close(); 
    } 
    catch(IOException ioe) 
    { 
     System.out.println(ioe.getMessage()); 
    } 
    System.out.println("File info received."); 

    ServerSocket fileTransferSocket = new ServerSocket(TRANSFER_PORT); 
    byte[] fileByteArray = new byte[filesize]; 
    try 
    { 
     Socket s = fileTransferSocket.accept(); 
     InputStream is = s.getInputStream(); 
     BufferedInputStream bis = new BufferedInputStream(is); 
     bis.read(fileByteArray, 0, fileByteArray.length); 
     s.close(); 
     FileOutputStream fos = new FileOutputStream(filename); 
     BufferedOutputStream bos = new BufferedOutputStream(fos); 
     bos.write(fileByteArray); 
     bos.flush(); 
     bos.close(); 
    } 
    catch(IOException ioe) 
    { 
     System.out.println(ioe.getMessage()); 
    } 
    System.out.println("Transfer complete!"); 
} 

客戶端代碼：

public class Client 
{ 
final static int FILEINFO_PORT = 1216; 
final static int TRANSFER_PORT = 1215; 
final static String SERVER_ADDR = "localhost"; 
static int filesize; 
static String filename; 

public static void main(String[] args) throws IOException 
{ 
    if(args.length != 1) 
    { 
     System.out.println("Usage: Client filename"); 
     return; 
    } 

    File file = new File(args[0]); 
    if(!file.isFile()) 
    { 
     System.out.println("File not found!"); 
     return; 
    } 
    filesize = (int) file.length(); 
    filename = file.getName(); 

    Socket fileInfoSocket = new Socket(SERVER_ADDR, FILEINFO_PORT); 
    try 
    { 
     OutputStream os = fileInfoSocket.getOutputStream(); 
     DataOutputStream dos = new DataOutputStream(os); 
     dos.writeInt(filesize); 
     dos.writeUTF(filename); 
     dos.close(); 
    } 
    catch(IOException ioe) 
    { 
     System.out.println(ioe.getMessage()); 
    } 

    Socket fileTransferSocket = new Socket(SERVER_ADDR, TRANSFER_PORT); 
    try 
    { 
     OutputStream os = fileTransferSocket.getOutputStream(); 
     BufferedOutputStream bos = new BufferedOutputStream(os); 
     FileInputStream fis = new FileInputStream(filename); 
     byte[] byteArray = new byte[filesize]; 
     BufferedInputStream bis = new BufferedInputStream(fis); 
     bis.read(byteArray, 0, byteArray.length); 
     bos.write(byteArray); 
     bos.flush(); 
     bos.close(); 
    } 
    catch(IOException ioe) 
    { 
     System.out.println(ioe.getMessage()); 
    } 
} 

在終端錯誤時，客戶端運行：

pratyush@SuperComputer:~/JP/NetworkFileTransfer/Server$ java Client "a.png" 
Exception in thread "main" java.net.ConnectException: Connection refused 
    at java.net.PlainSocketImpl.socketConnect(Native Method) 
    at  java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:345) 
    at  java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206) 
    at  java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188) 
    at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) 
    at java.net.Socket.connect(Socket.java:589) 
    at java.net.Socket.connect(Socket.java:538) 
    at java.net.Socket.<init>(Socket.java:434) 
    at java.net.Socket.<init>(Socket.java:211) 
    at Client.main(Client.java:54) 

Answer 1

不能exacly哪一行拋出異常，如果理解在fileTransferSocket上，也許fileTransferSocket沒有時間打開。儘量把睡在客戶端：

Thread.sleep(100); 

前：

Socket fileTransferSocket = new Socket(SERVER_ADDR, TRANSFER_PORT);