Application that can communicate with whatsapp

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http://stackoverflow.com – I want to develop an application which will communicate with whatsapp. What I mean is that, I have a CSV file which contains few cell phone numbers. My clients requirement is that, He will browse that CSV file through my application and whatsapp will send the messages on those numbers. This all will have to be done through Computers or via Cell Phone. Is there any possibility to do this? If there is then how can I reach to GOAL? I did some research on it, but unable to find. If it is possible then please help me to reach my goal. (HowTos)