Note:

The caller will only wait for a response inside the protocol converter, because the protocol converter is the only part of the system that can match a command with the printer's response.

If the last SplPdSendCmd has FLG_MORECMDS set and no new SplPdSendCmd is issued for the port driver's timeout, then the port driver should allow a job to be sent. This can happen only when there is a problem with the protocol converter.