Can't figure it out

I have probleme parsing binary data. As an example, the last character of the message in this example is "!" which should be coded in unicode by 0x21 but the input string end whith "00" for the last octet. What am I missing ?

assert (checkio(u'00317050201171820FD3323BDC0ED341C4303DEC3E8700') ==
        ['05 Jul 2013 02:11:17 GMT +7', 15, u'Selamat Datang!']), "Second Test, 7 bit"