flush

 public   void  flush()
            throws  IOException

    Flushes  this  output stream and forces any buffered output bytes to be written out. The general contract of flush is that calling it is an indication that,  if  any bytes previously written have been buffered by the implementation of the output stream, such bytes should immediately be written to their intended destination.

    The flush method of OutputStream does nothing.

     Throws :
        IOException -  if  an I/O error occurs.

...

    protected  OutputStream getOutputStream()  throws  IOException
   {
      if  (out ==  null )
        out =  new  SocketOutputStream();
      return  out;
   }
...