Write any protocol framing required for the subsequent call(s)
to sendBody(). This method does not actually write the message out on
the wire immediately. All writes happen at the end of the event loop
at the earliest.
@param length Length in bytes of the body data to follow.
Write any protocol framing required for the subsequent call(s) to sendBody(). This method does not actually write the message out on the wire immediately. All writes happen at the end of the event loop at the earliest. @param length Length in bytes of the body data to follow.