Send a websocket pong control frame.
void pong( ping_data const& payload, error_code& ec);
This function is used to send a pong frame, which is usually sent automatically in response to a ping frame from the remote peer. The call blocks until one of the following conditions is true:
The algorithm, known as a composed operation, is
implemented in terms of calls to the next layer's
function. WebSocket allows pong frames to be sent at any time, without
first receiving a ping. An unsolicited pong sent in this fashion may
indicate to the remote peer that the connection is still active.
The payload of the pong message, which may be empty.
Set to indicate what error occurred, if any.