Thank you Steve,
but what is the meanings of the “strange” characters I can see in the first 7 bytes ?
For example, each part of a long message is sent in XML as follows (the YYY… sequence is the text body part of the text I sent):
“é@oHt¿£YYYYYYYYY”
but the first 7 characters ? Apart from different values, it seems that the rules for the UDH reported from wiki should fit, at least at a semantical level.
Thanks again