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POPrintWriter vs DataOutputStream, weird behavior
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copied!<p>I'm creating a server/client model to send an image file from the server to the client. There's only ONE socket involved (all data are sent through it).<br> The server first sends the size of the image file, then sends the file data in bytes through a BufferedOutputStream. The client first receives the size of the file(size), creates a byte[size] imageBytes, then writes the received file data into imageBytes through a BufferedInputStream.</p> <p>Seems straight forward. The trouble happens when I send file size in different ways.</p> <p><strong>Way 1: using DataOutputStream and DataInputStream to send and receive file size as int.</strong></p> <p><strong>Way 2: using a PrintWriter to println(file size), then flush; using a BufferedReader to readLine().</strong></p> <p><strong>Way 1 works fine. But Way 2 sends the image file incorrectly.</strong> </p> <p>I wonder if this is because BufferedReader still keeps its buffer after reading, and the buffer is subsequently read by the BuffereInputStream.</p> <p>Here are the codes:</p> <p>Server:</p> <pre><code> package test; import java.io.BufferedInputStream; import java.io.BufferedOutputStream; import java.io.DataOutputStream; import java.io.File; import java.io.FileInputStream; import java.io.IOException; import java.io.PrintWriter; import java.net.ServerSocket; import java.net.Socket; public class TestServer { public static void main(String[] args){ try { ServerSocket serverSocket = new ServerSocket(9090); Socket ss = serverSocket.accept(); System.out.println("Client connected!"); File file = new File("ServerFiles/Songs/Covers/album1.jpg"); //Change this path to your own path BufferedInputStream bis = new BufferedInputStream(new FileInputStream(file)); byte[] imageBytes = new byte[(int) file.length()]; bis.read(imageBytes); bis.close(); //Way 1------------------------------------------------------------- DataOutputStream dos = new DataOutputStream(ss.getOutputStream()); dos.writeInt((int) file.length()); System.out.println("dos wrote "+file.length()); //End Way 1--------------------------------------------------------- //Way 2------------------------------------------------------------- // PrintWriter pw = new PrintWriter(ss.getOutputStream()); // pw.println(file.length()); // pw.flush(); // System.out.println("pw flushed!"); //End Way 2--------------------------------------------------------- BufferedOutputStream bos = new BufferedOutputStream(ss.getOutputStream()); bos.write(imageBytes); bos.flush(); System.out.println("bos flushed!"); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } </code></pre> <p>Client:</p> <pre><code> package test; import java.io.BufferedInputStream; import java.io.DataInputStream; import java.io.IOException; import java.net.InetAddress; import java.net.Socket; import java.net.UnknownHostException; import javax.swing.ImageIcon; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JPanel; public class TestClient extends JFrame{ Socket cs; ImageIcon imageIcon; public static void main(String[] args){ try { Socket socket = new Socket(InetAddress.getLocalHost(), 9090); new TestClient(socket); } catch (UnknownHostException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } public TestClient(Socket cs) throws IOException{ this.cs = cs; init(); } private void init() throws IOException{ imageIcon = getImageIcon(); JLabel jl = new JLabel(imageIcon); JPanel content = (JPanel) this.getContentPane(); content.add(jl); this.setSize(600,400); this.setVisible(true); } private ImageIcon getImageIcon() throws IOException{ //Way 1------------------------------------------------------------- DataInputStream dis = new DataInputStream(cs.getInputStream()); int size = dis.readInt(); System.out.println("size="+size); //End Way 1--------------------------------------------------------- //Way 2------------------------------------------------------------- // BufferedReader br = new BufferedReader(new InputStreamReader(cs.getInputStream())); // int size = Integer.parseInt(br.readLine()); // System.out.println("size="+size); //Print size //End Way 2--------------------------------------------------------- BufferedInputStream bis = new BufferedInputStream(cs.getInputStream()); System.out.println("bis.available()="+bis.available()); //Print bis.available() byte[] imageBytes = new byte[size]; bis.read(imageBytes); return new ImageIcon(imageBytes); } } </code></pre> <p>Outputs:</p> <p>Way 1:</p> <p>Server:</p> <pre><code>Client connected! dos wrote 23215 bos flushed! </code></pre> <p>Client:</p> <pre><code>size=23215 bis.available()=23215 </code></pre> <p>Way 2:</p> <p>Server:</p> <pre><code>Client connected! pw flushed! bos flushed! </code></pre> <p>Client:</p> <pre><code>size=23215 bis.available()=6837 </code></pre>

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