通过套接字发送图像

Question

i have a small problem sending image over Socket(client-server), i receive only "UTF" text but not the image object, is there something wrong with code?,

This code just sends the UTF txt and it's received on server side, i'm using the UTF text to identify an image(name) on server side and after identified it can send the image Object to client

    /*
     * ServerSide
     * 
     */
    package Interface_class;

    import configuraciones.procesador;
    import java.awt.image.BufferedImage;
    import java.io.DataInputStream;
    import java.io.DataOutputStream;
    import java.io.File;
    import java.io.IOException;
    import java.net.ServerSocket;
    import java.net.Socket;
    import java.net.SocketTimeoutException;
    import javax.imageio.ImageIO;

    /**
     *
     * @author TheCoder
     */
    public class img_monitor extends Thread{
            ServerSocket serverSocket;
           Socket server;
           BufferedImage bimg;
            byte[] bytes;
           public img_monitor() 
           {
               try{
//Opening server socket
              serverSocket = new ServerSocket(6066);
              System.out.println("Conectado al Socket!");
    }
               catch(IOException ex){
                   System.out.println("Error en: "+ex);

              }
           }

           public void run()
           {
//This class gets the path from a property file (works well)
            procesador obj = new procesador();
            obj.UBARCHIVO_CONFIG();

               while(true)
              {
                   try
                   {

                      server = serverSocket.accept();
                      System.out.println("Nuevo cliente conectado!");
                      DataInputStream din=new DataInputStream(server.getInputStream());
                      DataOutputStream dout=new DataOutputStream(server.getOutputStream());                 
    //Receiving image "name" from client as txt
                      String nombre = din.readUTF();
                      System.out.println(nombre);
//Using path+name of image to identify and send over socket
                      bimg = ImageIO.read(new File(obj.getRuta_arch_img()+nombre));
                      System.out.println(obj.getRuta_arch_img()+nombre);
                      ImageIO.write(bimg,"JPG",dout);
                      System.out.println("Image sent!!!");
    //                  server.close();

                      //lblimg.setIcon(img);
                  }
                 catch(IOException e)
                 {
                      e.printStackTrace();
                      break;
                 }
                 catch(Exception ex)
                {
                      System.out.println(ex);
                }
              }
           }

    }

Client Side

    /*
     * Client Side 
     * 
     */
    package Interface_class;

    import java.awt.image.BufferedImage;
    import java.io.DataInputStream;
    import java.io.DataOutputStream;
    import java.io.IOException;
    import java.net.ServerSocket;
    import java.net.Socket;
    import java.net.SocketTimeoutException;
    import javax.imageio.ImageIO;

    /**
     *
     * @author TheCoder
     */
    public class Obtener_imagen extends Thread {

        public Obtener_imagen() {
            System.out.println("Loading  Socket!");

        }

        public void run() {
//The class below gets info from database
            CLIENTINFO_CLASS obj = new CLIENTINFO_CLASS();
            obj.consulta();
            try {
                Socket socket = new Socket("localhost", 6066);
    //              DataInputStream din = new DataInputStream(socket.getInputStream());
                DataOutputStream dout = new DataOutputStream(socket.getOutputStream());
               //Using this to send image "name" to server, so it can identify and send image to client
 dout.writeUTF(obj.getImg_name());
                BufferedImage img = ImageIO.read(ImageIO.createImageInputStream(socket.getInputStream()));
                System.out.println("Image received!!!!");
    //                socket.close();
            } catch (IOException ex) {
                System.out.println("Error al abrir el socket" + ex);
            }
        }
    }

Answer 1

You aren't closing the socket after you send the image, so the client never stops reading. The server should close the socket output stream, and close the socket itself in a finally block.

The client should also close his socket, in a finally block.

EDIT: You don't need to use ImageIO to read and write the image files at the server, unless you are, say, changing the format. Just copy the bytes.

Answer 2

Following code i have wriiten a few days ago working for any kind of file/text (UI Support).Hope you can find it useful for solving your problem.In this example you server starts listening of specified port and Multiple clients can send data after server is started.

/**
Client sends the data
**/
import java.awt.BorderLayout;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.ObjectOutputStream;
import java.io.PrintWriter;
import java.net.Socket;

import javax.swing.JButton;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JTextField;


public class Client extends JFrame 
{

    JFileChooser fc;
    JButton browse;
    JPanel p1;
    private File file;
    JButton  upload;
    private final int SERVER_PORT=5000;
    private JTextField tf1;
    BufferedInputStream bis;
    BufferedOutputStream bos;
    PrintWriter pw;
    BufferedReader br;
    public Client() 
    {
        initGui();


    }
    public void initGui()
    {
        setSize(300,200);
        setResizable(false);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        browse=new JButton("browse");
        browse.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent arg0) {
                open();
                tf1.setText(file.getName());

            }
        });
        tf1=new JTextField();
        upload=new JButton("upload");
        upload.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent arg0) {

                try {
                    sendFile();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }

            }
        });
        add(tf1,BorderLayout.NORTH);
        p1=new JPanel();
        p1.setLayout(new FlowLayout(10,10,10));
        p1.add(browse);
        p1.add(upload);
        add(p1,BorderLayout.SOUTH);
        setVisible(true);


    }
    public void open()
    {
        fc = new JFileChooser();
        fc.showOpenDialog(this);
        file = fc.getSelectedFile();
        try {
            initNet();
        } catch (Exception e) {
            System.out.println("in initcatch");// TODO Auto-generated catch block
            e.printStackTrace();
        }

    }
    public void initNet() throws Exception
    {

        Socket s=null;
        try{
            setTitle("Startd Client");          
            s=new Socket("localhost",SERVER_PORT);
            bis=new BufferedInputStream(new FileInputStream(file));
            bos=new BufferedOutputStream(s.getOutputStream());
            pw=new PrintWriter(s.getOutputStream(),true);
            br=new BufferedReader(new InputStreamReader(s.getInputStream()));

        }catch(Exception e)
        {
            System.out.println("Error "+e);
        }finally{


        }
    }
    public void sendFile() throws IOException
    {
        pw.println(file.getName());
        int ch=bis.read();
        int counter=0;
        pw.println(file.length());
        while(counter<file.length())
        {
            bos.write(ch);
            System.out.println(ch);
            ch=bis.read();
            counter++;
        }

        System.out.println(ch);
        bos.write(ch);
        bos.flush();
        JOptionPane.showMessageDialog(null,br.readLine());

    }

    public static void main(String[] args) {
        try{
        Client c=new Client();
        }catch(Exception e)
        {
            System.out.println("in catch");
        }
    }
}

And the server:

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.ObjectInputStream;
import java.io.PrintWriter;
import java.net.*;
import java.util.ArrayList;
import java.util.Scanner;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;
public class Server extends JFrame
{
    private JButton start;
    private final int SERVER_PORT=5000;
    private ArrayList<Thread> thrdList;
    ServerSocket ss;
    Socket s;
    FileOutputStream fout;
    BufferedInputStream bis;
    BufferedReader br;
    Scanner sc;
    public Server()
    {
        initGui();

    }
    private void initGui()
    {
        setTitle("Server....");
        setSize(300,200);
        setResizable(false);

        start=new JButton("start");
        start.setBounds(10,20,20,20);
        start.addActionListener(new ActionListener() {
            public void actionPerformed( ActionEvent e )
            {

                try {
                    initNet();
                } catch (Exception e1) {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
                }
            }
        }
);
        add(start,BorderLayout.SOUTH);
        setVisible(true);
        addWindowListener(new WindowAdapter() {

            @Override
            public void windowClosing(WindowEvent arg0) {
                // TODO Auto-generated method stub
//              super.windowClosing(arg0);
                JOptionPane.showMessageDialog(null,"closed");
                try{

                if(br!=null)
                    br.close();
                if(bis!=null)
                    br.close();
                System.exit(0);
                }catch(Exception e)
                {
                    System.out.println("in cathch");
                }
            }

        });

    }
    public void initNet() throws Exception
    {

        thrdList=new ArrayList<Thread>();
        try{
            while(true)
            {
                ss=new ServerSocket(SERVER_PORT,1);
                while(true){
                    setTitle("Waitng for Client");
                    s=ss.accept();
                    MultiHandler mh=new MultiHandler(s);
                    thrdList.add(mh);
            }
            }

        }catch(Exception e)
        {
            System.out.println("Error in initNEt"+e);
        }finally{
            for(Thread t:thrdList)
                t.join();
            if(ss!=null)
                ss.close();
        }
    }
    class MultiHandler extends Thread
    {
        Socket sock;
        public MultiHandler(Socket s1) throws Exception
        {
            sock=s1;
            br=new BufferedReader(new InputStreamReader(s.getInputStream()));
            bis=new BufferedInputStream(s.getInputStream());
            System.out.println("Stream attached");
            start();
        }

        @Override
        public void run()
        {

            try {
                ClntHandler c=new ClntHandler(br,bis);

            } catch (Exception e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

        }
    }
    class ClntHandler extends Thread
    {
        BufferedReader br1;
        BufferedInputStream bis1;
        String filename;
        FileOutputStream fout;

        public ClntHandler(BufferedReader in,BufferedInputStream bis) throws Exception 
        {
            br1=in;
            bis1=bis;
            System.out.println("in clnthandler constr");
            start();
        }
        @Override
        public void run()
        {
            try{
                filename=br1.readLine();

                System.out.println(filename);
                fout=new FileOutputStream(filename);
                sc=new Scanner(s.getInputStream());
                int size=sc.nextInt();
                System.out.println("file created");
                int ch=bis.read();
                System.out.println(ch);
                System.out.println("after bis.read()");

                while(size>0)
                {
                    fout.write(ch);
                    System.out.println(ch);
                    ch=bis1.read();
                    size--;
                }

                System.out.println(ch);
                System.out.println("data written");
                PrintWriter pw1=new PrintWriter(s.getOutputStream(),true);
                pw1.println("DATA UPLOADED SUCCESSFULLY");


            }catch(Exception e)
            {
                System.out.println("Error"+e);
            }finally{
                if(fout!=null)
                    try {
                        fout.close();
                    } catch (IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }

                System.out.println("IN Finally");
            }
        }
    }
    public static void main(String[] args) {
        Server s=new Server();
    }


}

Answer 3

There is no separator between the image name Unicode string and actual binary image data. So I'm guessing the receiver will try to convert the entire received stream to string in:

String nombre = din.readUTF();

You can send the image name as a binary buffer with a size prefix, so your stream will look like:

[Number of bytes used for image name] [image name in binary] [image data]

Then read the first 4 bytes in X, read the next X bytes and convert to string for image name, read the rest for image data. Good Luck :)