code: public void invoke(String methodName, Object argument, OutputStream output) throws IOException {
  		invoke(methodName, argument, output, this.requestIDGenerator.generateID());
  	}
docs: Invokes the given method on the remote service passing
  the given argument.  An id is generated automatically.  To read
  the response {@link #readResponse(Type, InputStream)}  must be
  subsequently called.
  
  @param methodName the method to invoke
  @param argument   the arguments to pass to the method
  @param output     the {@link OutputStream} to write to
  @throws IOException on error
  @see #writeRequest(String, Object, OutputStream, String)