using jPOS to parse messages of serial port

Dear All,
I have previously also posted about reading and writing from serial 
port. Now since I have also looked at the jPOS again very recently, I 
have a new question. How can we pass the data read from serial port in 
hexadecimal format, and parse this via jPOS? As you know, the ISO 
message has many parts, there is also the header or TPDU, and there is 
bitmap which itself has a lot of meaning and each it signifies 
something, a component for example. Can you give me a good example of 
parsing a message such as this, provided we know the length and content 
of each field ?
Thank you in advance,
tasbihmr