Null characters in messages
UTF-8 Tcl, such as the Unicode standard, avoids the use of the zero-byte null but goes outside of the Unicode standard. It does this with the two-byte sequence 192, 128 to represent a null embedded in the UTF-8 string of the Tcl object. The null byte, with value zero, is reserved for string termination.
In the current byte mode, a message string can contain a null character as a non-terminator, and it can be manipulated using hciTcl commands. The UTF-8 implementation retains the null character as a zero-byte in the message string. This causes issues for user Tcl which uses the two-byte representation when the single-byte zero is required, retaining the limitations of string terminations in message strings.