Ravi> packet_type (1 byte unsigned) || packet_length (1 byte unsigned) || Ravi> packet_data(variable) Ravi> How to construct these using python data types, as int and float have Ravi> no limits and their sizes are not well defined. Take a look at the struct and ctypes modules. -- Skip Montanaro - skip at pobox.com - http://smontanaro.dyndns.org/