2719 ?The file handle supplied is not valid?.

FWIW, this usually means that the socket is already closed.

yes. by the time my connection::do_writeMessage() is called, socket_.is_open() returs false. but, why has it been closed and what the correct way to keep it open? i attempt to keep it open after writing the 1st response as follows: in connection::handle_writeResponse() call start(), which calls socket_.async_read_some() this is similar to the chat client sample. apparently that's not sufficient to keep the socket open for when i want to write to it again. fwiw, TcpView (from SysInternals) shows the socket's state as "established" after the 1st successful write and after the failed 2nd attempt. ???