DataOutputStream write() not working

Question

I have 2 devices connected via Socket

Server Code - (Android app):

log("sending song to client - " + clientSocket.getInetAddress().toString());

            InputStream fileInputStream = new FileInputStream(songFile);
            socketDataOutputStream.writeLong(songFile.length());
            Thread.sleep(50);
            byte[] byteBuffer = new byte[16 * 1024];
            int count;
            while ((count = fileInputStream.read(byteBuffer)) > 0) {
                socketDataOutputStream.write(byteBuffer, 0, count);
            }
            log("song sent to client - " + clientSocket.getInetAddress().toString());
            socketOutputStream.flush();
            log("sending a message to client - " + clientSocket.getInetAddress().toString());
            socketDataOutputStream.writeUTF("play");
            log("message sent to client - " + clientSocket.getInetAddress().toString());

Client Code - (PC code):

OutputStream fos = new FileOutputStream(song);
        InputStream sis = socket.getInputStream();
        DataInputStream dis = new DataInputStream(new BufferedInputStream(sis));
        long size = dis.readLong();
        int count;
        log ("Receiving file");
        while (size > 0 && (count = dis.read(buffer, 0, (int) Math.min(buffer.length, size))) != -1) {
            fos.write(buffer, 0, count);
            size = size - count;
        }
        fos.close();
        log ("File received");
        String s;
        while ((s = dis.readUTF()) != null) {
            log(s);
        }

The Song is successfully received but after that no communication with the socket is possible! I have tried different ways - PrintWriter, write(bytes[]). Nothing happens - the client side code does not enter the second while loop.

I don't understand what wrong I'm doing.

Answer 1

while ((s = dis.readUTF()) != null) {
        log(s);

Remove this. It doesn't make sense. readUTF() doesn't return null, and you shouldn't be just throwing input away.

If this is supposed to be receiving the "play" command, you should store one readUTF() result into a String and then compare it to "play" properly. But the command is redundant. You can play it as soon as you've finished receiving it, and you know when that is.

The sleep is literally a waste of time. Remove that too.