The IsWritable property returns True if data can be written
to the current client socket without blocking. If the
IsWritable property returns False, this means that the
application cannot write to the socket at that time. However, if the
property returns True, this does not guarantee that you will be able
to write to the socket without an error. The next socket operation
may result in a swErrorOperationWouldBlock or
swErrorOperationInProgress error. The application should treat
these errors as recoverable, and should be prepared to retry
operations that result in them.
The value of this property is only meaningful inside an event
handler such as OnRead or OnWrite.