The system sends an ENQ character to the PMS and awaits a reply. If no response is received within the time-out period of 3 seconds, the ENQ is retried 19 times before abandoning the transmission of the message (a total of 20 times and an elapsed time of 1 minute). The system generates a hotel log and an alarm indicating the PMS is down. The system then attempts to re-establish communication by sending an ENQ every three seconds.
If a NAK (negative acknowledgment) character is received by the system, the ENQ is retried 19 times before abandoning transmission. When a NAK is returned, the PMS is working, but is busy. The system generates a hotel log and an alarm indicating the PMS is down, and continues to send an ENQ. The actions taken by the system when the PMS is down or busy are the same.
When the PMS is able to respond with an ACK, the system generates a Hotel PMS log for PMS is up.
If an ACK (acknowledgment) is received within three seconds of an ENQ, the transmission continues.
The system sends a start-of-text (STX) character, the message text, and an end-of-text (ETX) character to the PMS. It then awaits an ACK from the PMS.
If no response is received within the time-out period (3 seconds) the entire sequence, beginning with the ENQ, is retried 4 times (for a total of 5 attempts and an elapsed time of 15 seconds) before abandoning transmission. The system generates a hotel log and an alarm to indicate that the PMS is down. The system returns to the situation when the PMS is down and continues to send the same transaction.
If a NAK is received, the complete sequence beginning with ENQ is retried 4 times before abandoning transmission. The system then generates a hotel log to indicate that the PMS refuses to accept the transaction. The transaction is then given up and discarded, and the system tries to send the next transaction.
If an ACK is received, transmission is completed successfully.
Notes:
If the system determines that the PMS link is down, an alarm is raised and presented on the console, along with a hotel log. This is handled by the central hotel process. This is not a maintenance alarm; this is a separate alarm noting 'PMS FAILURE'.
The 3300 ICP, whether as part of a Hospitality cluster or as a standalone system, supports one PMS connection at a time. Any other PMS transactions attempted will not receive a response until the current transaction is completed. If the PMS transaction times out while waiting for a response, a hotel log will be generated.
PMS transactions attempted on devices hosted on a Hospitality ICP that is down are acknowledged but not executed. Each attempt generates a hotel log at the Hospitality Gateway.
PMS attempts to add an STS-disabled suite to the Hospitality Gateway has no effect
After receiving an ENQ character from the PMS, the system responds within three seconds with either an ACK or a NAK. The ACK indicates the transmission was successful. The NAK indicates there was a transmission error, or that the system is busy. The system generates a hotel log indicating such an error occurred. After sending the ACK, the system is immediately ready to receive the STX, message text, and ETX. Within three seconds of receiving the ETX, it responds with either:
ACK indicating the transmission was successful, and all of the message fields are valid.
NAK indicating there was an error in either the transmission itself, in one of the message fields, or in the syntax of the message (specifically STX, ETX, function code and status code; for example, CHK3 is sent instead of CHK1). The system generates a hotel log indicating this error occurred. The PMS is able to retry sending only the message txn (STX, message text and ETX) three more times without prefacing it with an ENQ message first.
An example of a PMS retry is:
The PMS then discards the transaction.
If the PMS and system both want to send a transaction at the same time, the PMS always permits the system to go first.
For example:
After the system is finished, the PMS then continues to send its own transaction.
When the communication link is not busy between the two machines, the PMS will automatically send an ENQ to ensure the system is still up and functioning correctly. The system is expected to reply within three seconds. If it replies with an ACK, the PMS sends an Are You There? message. The system is expected to reply with an ACK within three seconds. For example:
