Before downvoting, please note that I am only asking for expert opinion, and not the source code.
I am working on an android app which will sync contacts/sms/mms on a webserver.
Which of the web service technologies is suitable for this app and easy to parse on server side?
Is it correct to convert contacts etc to a text file before sending to the server as I may not be able to convert mms and picture messages to a text file?
I want users to restore their data from the server. Will there be any problem regarding data format while downloading data to mobile?
REST web services are generally the best way to go for mobile devices as they are light weight meaning they require less processing and phone resources to use when parsing responses in JSON.
Heres a link to a question that deals with accepting an attachment over a REST web service in java
How do I write a restful web service that accepts a binary file (pdf)
However REST isn’t as secure as SOAP, given its going to be personal data you may want to consider this. Also from experience of whats been happening in the news with this kind of data being taken off of phones you may want to consider not doing this at all as it can become a data privacy law nightmare.