Write data to a serial port.
Send this command to an operator to write the given data to its associated serial port.
An acknowledgment may be set, in which case it is sent back to the sender on a successful write.
Note that a successful write does not guarantee the actual transmission of data through the serial port,
it merely guarantees that the data has been stored in the operating system's kernel buffer, ready to
data to be written to port
acknowledgment sent back to sender once data has been enqueued in kernel for sending (the acknowledgment
is a function 'number of bytes written => event')