Building C language's binary protocol strings in Java

[Siamak Saarmann]

Hello,

One of my fellow researchers (a C/C++ developer) was assigned to design a protocol and because he is a C programmer he designed something which is hard to implement in other languages which we need (VB, php, Java, C#).

If it had built something like SMTP and HTTP protocol (where even numbers are transferred in string format) it could be easily implemented. However he has used C structures.

<magic_numbers> <data_size> <protocol_version> <connection_id>
<serial_number> <compression> <res_1> <res_2> <res_3> <res_a> <res_b>
<message_body>
 
magic_numbers : four characters, which can be :
VDCM : message from client to server.
VDSM : message from server to client.
 
data_size : a 32-bit unsigned integer containing the total message size
(the length of the message_body + 32).
 
protocol_version : a 32-bit unsigned integer containing the protocol version.
8-bit 8-bit 8-bit 8-bit
major minor revision fix
 
connection_id : a 32-bit unsigned integer containing the connection ID
(ignored for some messages).
 
serial_number : a 32-bit unsigned integer containing the message serial
number (a sequence number generated by the client).
 
compression : an 8-bit unsigned integer defining the compression type of
the message body.
 
res_1, res_2, : an 8-bit unsigned integer, reserved for future expansion.
res_3
 
res_a, res_b : a 32-bit unsigned integer, reserved for future expansion.
 
message_body : variable length bytes containing the real message (can be
compressed and/or symmetrically encrypted).

1) Now the problem is that how can I create such commands (which contain binary coded numbers with different lengths) in Java?

2) What primitive data types I should use for 8bit and 32bit unsigned data types (in a way that later a C program does not have problem interpreting them as normal C data types)?

Thank you for your help.
Mac

[Ernest Friedman-Hill]

You should have no problem writing and reading this with DataOutputStream/DataInputStream. The signed/unsigned issue won't be a problem if handled carefully.