Binary SMS
In this chapter we discuss how you can use SMS messages for more complex tasks than just short texting. By using binary SMS and various binary protocols and extensions based on binary SMS, it is possible to send and receive many different types of messages over SMS: long text messages, rich text or multimedia messages, calendar entries, address book contact items, and others.
We start by discussing the general framework used by binary SMS messages, and then examine the various specific types of binary SMS messages that are possible and commonly used. The most complex type is probably WAP Push, due to the number of protocols and technologies involved, and because of its importance I’ll dedicate a separate chapter to it.
What is a Binary SMS Message?
We have seen how in GSM networks you can send text data (encoded using the GSM alphabet or UCS-2) in an SMS message. It is also possible to flag the message as a binary SMS and send arbitrary 8-bit binary data in it, or to add a binary “User Data Header” (UDH) at the beginning of the message to transmit special information about the message (how to build and use a UDH will be discussed in the following sections).
Binary data and UDHs are often used in combination, with the message containing binary data and the UDH giving instructions about how to interpret the binary data. In fact, a message that contains 8-bit binary data with no information about how to interpret it is not very useful, so nearly all messages containing binary ...
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