Assigns read, write and event(status) callbacks
$readcb
$writecb
$eventcb
$arg
Assigns read, write and event(status) callbacks.
readcb
Read event callback. See About buffer event callbacks .
writecb
Write event callback. See About buffer event callbacks .
eventcb
Status-change event callback. See About buffer event callbacks .
arg
A variable that will be passed to all the callbacks.
値を返しません。