SBN/doc/cfs_sbn.md says that the MsgSz field is "The total size of the message, including this header." However, a code inspection of SBN_PackMsg seems to indicate this field reflects the payload size. This seems to be confirmed with a sim that implements the SBN protocol talking to the app breaking when implemented with the field being the total size and working with the field being the payload size.
SBN/doc/cfs_sbn.mdsays that theMsgSzfield is "The total size of the message, including this header." However, a code inspection ofSBN_PackMsgseems to indicate this field reflects the payload size. This seems to be confirmed with a sim that implements the SBN protocol talking to the app breaking when implemented with the field being the total size and working with the field being the payload size.