The OnWrite event is generated when the client can accept
data from the server. The Handle argument specifies the handle
to the client socket and can be used in conjunction with the
Write or WriteLine methods.
This event is typically fired once when the client connection is
established with the server, the session thread starts and the client
socket enters a writable state. If the internal send buffer for the
client socket becomes full, this event will fire again when more data
can be written to the socket. It is important to note that this event
is level-triggered and will not fire repeatedly if the client socket
is writable. Under most circumstances this event fire only once for
each client session after the initial connection has been
established.