Send & Receive MDNs

Message Disposition Notifications or MDNs are return receipts used to notify the sender of a message of any of the several conditions that may occur after successful delivery. In the context of the AS2 protocol, the MDN is used to notify if the message was successfully processed by the receiver’s system or not and in case of failures the reason for the failure is sent with the MDN.

MDNs can be transmitted either in a synchronous manner or in an asynchronous manner. The synchronous transmission uses the same HTTP session as that of the AS2 message and the MDN is returned as an HTTP response message. The asynchronous transmission uses a new HTTP session to send the MDN to the original AS2 message sender.

Send MDNs

The choice of whether to send an MDN and its transfer mode is with the sender of the AS2 message. The sender lets us know what to do through an AS2 header field. In case the partner requests a synchronous MDN no action is needed as pyAS2 takes care of this internally, however in the case of an asynchronous MDN the admin command sendasyncmdn needs to be run to send the MDN to the trading partner.

The command {PYTHONPATH}/python {DJANGOPROJECTPATH}/ sendasyncmdn should be scheduled every 10 minutes so that pyAS2 sends any pending asynchronous MDN requests received from your trading partners.

Receive MDNs

The choice of whether or not to receive MDN and its transfer mode is with us. The MDN Settings for the partner should be used to specify your preference. In case of synchronous mode pyAS2 processes the received MDN without any action from you.

In the case of asynchronous mode we do need to take care of a couple of details to enable the receipt of the MDNs. The global setting MDNURL should be set to the URL http://{hostname}:{port}/pyas2/as2receive so that the trading partner knows where to send the MDN. The other setting of note here is the ASYNCMDNWAIT that decides how long pyAS2 waits for an MDN before setting the message as failed so that it can be retried. The admin command sendasyncmdn makes this check for all pending messages so it must be scheduled to run regularly.