Thread Synchronization problem

Question

We guys are developing a P2P file sharing software(on LAN) and our program requires that we implement a multi-threaded client. I somewhere read on the forum about a multi threaded server but it doesnt work in my case (not on the client side.)The program runs properly when a single transfer is happening but if more then one file is getting downloaded the program seems to fall apart. Here's the code that provides the client side implementation of a file transfer.
class Down implements Runnable     
                     DataOutputStream dataOutput;     
                     BufferedInputStream bufferedInput;     
                     FileOutputStream fileOutput;
                     Socket down;
                     public void run()
                                  try
                                          int data=0;
                                          long i=0;
                                          down=new Socket(user,9999);
                                          dataOutput=new DataOutputStream(down.getOutputStream());  //The following two lines send the file path to the server, to make the server's job easier rather than the server going for a file search
                                          String msg=path.replace('\\','/');   dataOutput.writeUTF(msg);     
                                          dataOutput.flush();
                                          bufferedInput=new BufferedInputStream(down.getInputStream());
                                          fileOutput=new FileOutputStream(new File(path));
                                          while (data != -1)
                                                   data=bufferedInput.read();
                                                   fileOutput.write(data);
                                                   fileOutput.flush();
                                                   i++;
                                                   System.out.println("Transferring "+i);
                                          System.out.println("File Transfer Done");
                                          done=true;
                                 catch (Exception e)
                                             e.printStackTrace();
                                 } Can you guys point out specifically where my program would need synchronization, since im a noob when it comes to threads. Thanks

Answer 1

Thanks ejp for those prompt replies .......yeah the path and the down socket) variables are unique...... from what i see on my network .... the server side of the transfer happens at a faster rate i.e the final println line printing the transferred byte (at the end of the while loop) is much ahead at the server side of the transfer ...... the client lags far behind in this regard...... and from what i know Lan connections support upto 100Mbps so there's no question of data loss..... one of the reasons i opted for byte by byte transfer....... just to be on the safer side...... and yes ill make that small change in my program