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All exchanged operations (OC) return a feedback to the sender. This ACK message is designed to confirm that the receiver has received the message and is now in charge of the further processing.

Operationcode: ACK



IF Partner → SIHOT.PMS

SIHOT.PMS → IF Partner


The answer could look like:

<?xml version="1.0" encoding="ISO-8859-1"?>
  <MSG>room not occupied</MSG>

Attributes Message

Attribute Denotation Type
OC ACK String
TN Transaction Number uns. Long.
RC Return Code. Here we refer to the content of the MSG tag. uns. Long
MSG Message text, error message in plain text (optional) String
ORG Origin, this is the identifier of the SIHOT workstation that processed this operation. String

If an operation used the <TN> tag, this tag has also to be returned to the sender. The same procedure applies to the <ORG> tag.


The external system needs to wait until it receives the ACK or until the socket is disconnected. Should the socket be disconnected, the external system can assume a crash of the interface and handle this as an ACK with an error code.

If the external system nonetheless needs to use a timeout how long it waits for the ACK, this timeout should at least be one minute. Our system is a server where many processes interact and not a real time server just for this interface. Normally, the ACK will be sent within a second but it might even take longer than a minute depending on system load and database access by other services or users.

Should the external system deny a service since its timeout ended before the ACK on the posting record was received, it still needs to process the ACK when it comes later.

E.g. if a Pay-TV system sends a posting and its timeout ended before it receives the ACK, it may decide not to show the movie. If it receives the ACK later and the RC is 0, this means the posting was done correctly in SIHOT. Since the movie was not shown, the Pay-TV system should send a cancellation of the posting immediately. Alternatively, it needs at least to show and log this problem.