Forwarding data from one client to another using server

I am creating an android application which uses wifi direct to transfer data. I am able to send data from client to server. I want to send data from one client to another client through server. Let us suppose there are two clients A and C and a server B. I want to send data from A to C through B. Is there any possible way to achieve this task. One thing I had heard is forward data from input stream of one socket ouput stream of another. Can anyone please help me out with this.

` protected String doInBackground(Void... params) {
            try {
                ServerSocket serverSocket = new ServerSocket(8988);
                Log.d(WiFiDirectActivity.TAG, "Server: Socket opened");
                Socket client = serverSocket.accept();
                Log.d(WiFiDirectActivity.TAG, "Server: connection done");
                final File f = new File(Environment.getExternalStorageDirectory() + "/"
                        + context.getPackageName() + "/wifip2pshared-" + System.currentTimeMillis()
                        + ".jpg");

                File dirs = new File(f.getParent());
                if (!dirs.exists())
                    dirs.mkdirs();
                f.createNewFile();

                Log.d(WiFiDirectActivity.TAG, "server: copying files " + f.toString());
                InputStream inputstream = client.getInputStream();
                copyFile(inputstream, new FileOutputStream(f));
                serverSocket.close();
                return f.getAbsolutePath();
            } catch (IOException e) {
                Log.e(WiFiDirectActivity.TAG, e.getMessage());
                return null;
            }
        }`