A standard SMS message will send messages of at most 160 7-bit characters to a recipient. But what is the message to be sent is longer than this. The PDU SMS protocol allows for this and the message is split into many SMS messages and then combined back together by the receiver. These are called long or concatenated SMS messages. When the message to be sent is longer than 160 7-bit characters then the client messaging app will split the message and send these part messages as indiidual SMS messages.
In the SMS message header the second octlet is set to 11 for an SMS message, this is changed to 41 for a concatenated or long SMS message, on each of the SMS messages making up the long message.
|05||Length of the header|
|00||Type of Message|
|03||Length of header data|
|A6||Unique number for SMS message|
|02||How many parts|
The sending App splits the long message into the correct number of SMS messages and sends these as individual SMS messages. A long SMS comprising 3 normal SMS messages will be charges as 3 messages. The receiving app will receive the individual SMS messages, and piece together the full long message for display on the receiver's device.
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