Thread: How to transfer data structures over net ?

Howdy ,
I'm working on a project that the server will be developed using C and run on linux , while the clients will be running on mobile phones and small pc's .

This is a study project (to learn QT embedded and more) so here is the deal .
I need to transfer data structures from the server to clients ,

I read about soap while it looked fine i realized it is abit problematic (over kill) i played abit with transferring structures using network sending but here the serialization issue arises.

Thanks in advance ,

i would use tcp or udp sokets. Just remember that in embedded world people often use big endianess targets, and when negotiating with pc, one needs to handle conversions.

when you do not know possible OS/language on the receiving size - serialization is best approch IMHO

you do not need to serialize to xml though, text string with suitable separators is enough...

just make sure that choosen separators could not be part of the data on any locale settings

For example I would not use . or , as separators as they could be part of the number string representation

if your data could include date/time - symbols like \ / : - # are also out of the scope

I agree, the most obvious solution is to simply make the data into a text-string and transfer that. It solves all problems with byte-order, padding and sizes of data types that commonly happen when one tries to transfer data across the net.

Another option to "avoid anyting that could be part of your content" is to use a quoted or escaped method. For example, we use : as a separator. Strings that may contain : will have to be quoted (using either single 'xxx' or double quotes "xxx"), or escapted, for example using the C style convention of a backslash: The text "15:45" then converts to "15\:45". Obviously, just like C, backslash itself also needs to be escaped.

Even if you use XML, you will need some way to describe things that are part of the XML syntax (such as < and >).

--
Mats

Oh, so we were talking about protocols, sorry. If the amount of sent structures is fixed, it is possible to build send\recv with simple method. Append each sent struct with the size. Add some identification number to structs. Fix the endianess to certain format, or add the endianess info to the beginning of message.