Question

I have a case where the client after establishing a connection with the server, receives one file and when the same connection was used ( persistent ) I end up getting this error mentioned above.
Below is the implemented code:

Scanner in = new Scanner(file);

this.clientSocket = new Socket(this.host,this.port);

this.os = new DataOutputStream(this.clientSocket.getOutputStream());

this.is = this.clientSocket.getInputStream();

while(in.hasNextLine()){
  newFile = in.nextLine();
  System.out.println(newFile);

  this.os.writeBytes(newFile + '\n');
  this.os.flush();
  scanFileList();
  writeFile();

 }

and the server side implementation is:

 final class HttpRequest implements Runnable {
   final static String CRLF = "\r\n";
   Socket socket;
   static String dir;
   BufferedOutputStream outToClient = null;
   // Constructor
   public HttpRequest(Socket socket) throws Exception {
      this.socket = socket;
      dir = "C:\\Users\\";
 }


      // Implement the run() method of the Runnable interface.
 public void run() {
     try {

       // Get a reference to the socket's input and output streams.
       InputStream is = socket.getInputStream(); 
       outToClient = new BufferedOutputStream(socket.getOutputStream());
       processRequest(is,outToClient);
         } catch (Exception e) {
               System.out.println(e);
         }
 }

private void processRequest(InputStream is,BufferedOutputStream os) throws Exception {

    // Set up input stream filters.
    BufferedReader br = new BufferedReader(new InputStreamReader(is));

    // Get the request line of the HTTP request message.
    String fileName = br.readLine();



    // Prepend a "." so that file request is within the current directory.
    System.out.println(fileName);
    // Open the requested file.
    File myFile = null ;

    boolean fileExists = true ;

    myFile = new File(dir + fileName);

    FileInputStream fis = null ;
    try {
      fis = new FileInputStream(dir + fileName);
      System.out.println(fis);
    } catch (FileNotFoundException e) {
        fileExists = false ;
    }

    // Debug info for private use
    System.out.println("Incoming!!!");


   // Send the entity body.
   if (fileExists) {
    sendBytes(myFile, os);
    //fis.close();
   } 
   // Close streams and socket.
   is.close();
   os.close();
   br.close();
   socket.close();
   }

   private static void sendBytes(File myFile, 
    BufferedOutputStream os) throws Exception {
         // Construct a 1K buffer to hold bytes on their way to the socket.
         byte[] mybytearray = new byte[(int) myFile.length()];


         FileInputStream fis = null;
         // Copy requested file into the socket's output stream.
         try {
           fis = new FileInputStream(myFile);
         } catch (FileNotFoundException ex) {
            // Do exception handling
         }
         BufferedInputStream bis = new BufferedInputStream(fis);

         try {
           bis.read(mybytearray, 0, mybytearray.length);
           os.write(mybytearray, 0, mybytearray.length);
           os.flush();

           // File sent, exit the main method
           return;
         } catch (IOException ex) {
         // Do exception handling
           }
        }

   }

The error happens when the program on the client side tries to write to the server through: this.os.writebytes(newFile + /n);

  Testfile01.bmp

  writing

  saved

  Testfile02.bmp

Exception in thread "main" java.net.SocketException: Socket closed
at java.net.SocketOutputStream.socketWrite(Unknown Source)
at java.net.SocketOutputStream.write(Unknown Source)
at java.io.DataOutputStream.writeBytes(Unknown Source)
at TCPClientPersistentNp.openSocket(TCPClientPersistentNp.java:53)
at TCPClient.main(TCPClient.java:66)

Answer 1

I’m not going to try to read your code in detail (see comment above …), but there is clearly something very strange / wrong about it.

Put simply, if you are going to talk to an HTTP-based server, you can’t just open a socket and write stuff. Your client has to create well-formed HTTP requests, and process the HTTP responses that come back.

The exception on the client-side is happening because the server side … in fact YOUR CODE … has closed the connection at the other end.