retryTimerValue is the current value of the retry timer for
this connection; it indicates the number of seconds before
the next connection attempt will be made. retryTimerValue
is initialised when a connection attempt fails.
When retryTimerValue reaches 0, an attempt will be made
to establish the connection.
When the timer is not running, for example when the
connection has been established, retryTimerValue will be
0.