Send download link of a file after Bitcoin payment I'm starting an online business. My website is hosted on OVH I would like to send a download link after a bitcoin payment.

Are there specific stuffs I should be aware of?
Is this difficult to develop? (I have a bit of experience with JS, JAVA HTML/CSS) but I don't really knwow where to start with the GET... commands.
Is it safe to store the file directly on my FTP?
Do external websites already provide this kind of services (payment and download)?
What could be the best language to use with the blockchain api?


just to be more specific:

the scheme of the whole think would be:

user: I'm interested in your product.
server: Please pay for it with your bitcoins.
user: I'll do that I'll go on your dedicated page.
server: Ok we received your payment you just received a link for you to download our file.
user: thanks it worked!!!


your help is appreciated many thanks in advance,
You do not need to deal directly with the blockchain. The answer is:
Payment Gateways
There are services called Payment Gateways that encapsulate the entire invoicing/payment process and allow you to check on the status of each payment (manually or programmatically) to offer your goods.
One such example for bitcoin is Bitpay. Bitpay provides you with a RESTful API which you can call/query for information retrieval and/or for the execution of specific orders/transactions. You can find all the details in this API reference
As far as the implementation goes, Bitpay provides you with numerous clients in different programming/scripting languages, namely: PHP, python, Node.js, Ruby, Java, C# etc...
There are many bitcoin payment gateways available with different offerings and pricing schemes. Do some research to find the one most suitable for your budget and task.
Is it difficult to accomplish? Not necessarily. However, this is highly dependent on your level of skill and knowledge in programming specifically web development.
I would also recommend you hire a specialist to do this for you if your grip on security is not so well, since security is one of the major concerns when dealing with financial transactions.