A multithreaded client server program to download image files. If you want to execute it on your machine you should change the file paths. Since there are four files to download the client makes the same number of connection attempts. The files sent by the FileServer will get repeated after the fourth connection attempt. In the File Server client app the file saving is done in new threads so as to not hamper the file downloading process. There is little interaction between client-server. Here is the FileServer...public class FileServer {    private final ExecutorService exec = Executors.newCachedThreadPool();    final String[] fileNames = {            C:\\Users\\clobo\\Pictures\\Ex1.jpg,            C:\\Users\\clobo\\Pictures\\Ex2.jpg,            C:\\Users\\clobo\\Pictures\\Ex3.jpg,            C:\\Users\\clobo\\Pictures\\Ex4.jpg    };    public void start() throws IOException {        ServerSocket socket = new ServerSocket(7777);        System.out.println(Waiting for client message...);        while (!exec.isShutdown()) {            try {                for (final String fileName : fileNames){                     final Socket conn = socket.accept();                    exec.execute(new Runnable() {                        public void run() {                            sendFile(conn,fileName);                        }                    });                }            } catch (RejectedExecutionException e) {                if (!exec.isShutdown())                    log(task submission rejected, e);            }        }    }    public void stop() {        System.out.println(Shutting down server...);        exec.shutdown();    }    private void log(String msg, Exception e) {        Logger.getAnonymousLogger().log(Level.WARNING, msg, e);    }    public void sendFile(Socket conn, String fileName) {        File myFile = new File(fileName);        if (!myFile.exists()) {            log(File does not exist!,null);        }        // file does exist        System.out.println(Thread.currentThread().getName());        System.out.println(AbsolutePath: + myFile.getAbsolutePath());        System.out.println(length:  + myFile.length());        if (myFile.exists()) {            try {                ObjectOutputStream oos = new ObjectOutputStream(                conn.getOutputStream());                oos.writeObject(myFile);                oos.close();            } catch (IOException e) {                log(IOException Error, e);                e.printStackTrace();            }        }    }    public static void main(String[] args) throws IOException {        FileServer fs = new FileServer();        fs.start();    }}here is the FileServerClient...public class FileServerClient {    private final ExecutorService exec = Executors.newCachedThreadPool();    Frame myFrame = new Frame();    List<File> fileList = new ArrayList<File>();    public void receiveFileFromServer() throws Exception{        Socket sock = null;        InputStream socketInputStream = null;        String host = localhost;        int port = 7777;        for (int i=0;i<4;i++) {            sock = new Socket(host, port);            socketInputStream = sock.getInputStream();            System.out.println(Connection successful...);            // recieve the file            ObjectInputStream ois = new ObjectInputStream(socketInputStream);            // file from server is deserialized            final File myfile = (File) ois.readObject();            fileList.add(myfile);            // deserialized file properties             System.out.println(AbsolutePath:  + myfile.getAbsolutePath());            System.out.println(FileName: + myfile.getName());            System.out.println(length + myfile.length());            exec.execute(new Runnable() {                public void run() {                    saveFile(myfile);                }            });        }    }    private void saveFile(File myfile) {        FileDialog fileDialog = new FileDialog(myFrame,                Choose Destination for + myfile.getName(), FileDialog.SAVE);        fileDialog.setDirectory(null);        fileDialog.setFile(enter file name here);        fileDialog.setVisible(true);        String targetFileName = fileDialog.getDirectory()                + fileDialog.getFile() + .jpg;        System.out.println(File will be saved to:  + targetFileName);        copyBytes(myfile, targetFileName);    }    private void copyBytes(File originalFile, String targetFileName) {        try {            FileInputStream in = new FileInputStream(originalFile);            FileOutputStream out = new FileOutputStream(targetFileName);            int c;            while ((c = in.read()) != -1) {                out.write(c);            }            out.close();            in.close();        } catch (Exception e) {            log(IOException Error, e);        }    }    private void log(String msg, Exception e) {        Logger.getAnonymousLogger().log(Level.WARNING, msg, e);    }    public static void main(String[] args) throws Exception {        FileServerClient client = new FileServerClient();        client.receiveFileFromServer();    }}
Multithreaded Client-Server file downloading application
java;multithreading