SMS Delivery Reports with SMPP protocol

There are two ways to verify the delivery of SMS messages.

• Query the status of the message
• Request delivery reports from the provider

Query the status of the message

When a message is send using the SMPP protocol, the provider returns a message reference. Using this reference, we can query the provider for the delivery status of this message. This is done by sending a 'query_sm' packet to the provider. If the message reference is known by the provider, it responds with a 'query_sm_resp' packet. This packet holds the status of the message. This can be one of the following values:

Status Number	Status	Explanation
0	SCHEDULED	The message is scheduled for later sending.
1	ENROUTE	The message is enroute.
2	DELIVERED	The message was successfully delivered.
3	EXPIRED	The SMSC was unable to deliver the message in a specified amount of time.For instance when the phone was turned off.
4	DELETED	The message was deleted.
5	UNDELIVERABLE	The SMS was unable to deliver the message.For instance, when the number does not exist.
6	ACCEPTED	The SMS was accepted and will be send.
7	UNKNOWN	Unknown error occured.
8	REJECTED	The message was rejected.The provider could have blocked phonenumbers in this range.
9	SKIPPED	The message was skipped.

The disadvantage of this method is, that you have to poll once in a while to get the current message status. When a lot of messages are enroute for a couple of hours, this will cause heavy data traffic. Most providers recommend you to request delivery reports instead of querying, because there is only data sent by the provider when the status of a message has changed.

Request delivery reports from the provider

The best way to check the status of each message sent, is to ask for delivery reports. This can be done by setting the 'registered_delivery' value of the 'submit_sm' packet. This parameter can have one of the following values:

Value	Meaning
0	Do not send delivery reports
1	Always send delivery reports
2	Send delivery report in case of an error
3	Send delivery report only when message is delivered

By setting this value to '1', the provider will send a delivery report to the client every time the status of this message changes. You can set this value per message.

The delivery reports are sent to the client using the 'deliver_sm' packet. This is the same packet as used to deliver incoming messages. To detect whether a 'deliver_sm' is a delivery report or a message, you have to check the 'esm_class' field. If bit 2 of this byte is set ( 0x04 ), it is a delivery report. To use delivery reports, you have to setup a transceiver connection to the SMPP provider, because you are going to send and receive messages. The delivery status is encoded in the 'short_message' field as an ASCII text message. This format is product specific, but the following format is used by most SMPP providers:

id:c449ab9744f47b6af1879e49e75e4f40 sub:001 dlvrd:0 submit date:0610191018 done date:0610191018 stat:ACCEPTD err:0 text:This is an Acti
id:7220bb6bd0be98fa628de66590f80070 sub:001 dlvrd:1 submit date:0610190851 done date:0610190951 stat:DELIVRD err:0 text:This is an Acti
id:b756c4f97aa2e1e67377dffc5e2f7d9b sub:001 dlvrd:0 submit date:0610191211 done date:0610191211 stat:REJECTD err:1 text:This is an Acti
id:bd778cd76ae9e79da2ddc8188c68f8c1 sub:001 dlvrd:0 submit date:0610191533 done date:0610191539 stat:UNDELIV err:1 text:This is an Acti

Field	Meaning
id	The message reference of the message.
sub	Sub-ID, not used.
dlvrd	Value '1' when the message has been delivered, if the message is still pending '0'.
submit date	Submission date and time.
done date	Date and time the status has changed, or message delivery time when stat is set to 'DELIVRD'.
stat	Current status of the message.
err	Additional error code, provider specific.
text	Part of the original message text.

When using SMPP version 3.4, sometimes the message has some optional parameters (TLV's) attached containing the message state, message reference and a network error code. Please refer to the SMPP version 3.4 documentation on how to use these TLV's.