How to correctly send an in-app subscription receipt via Http Request?

I want to send the receipt got from AppStore after an in-app subscription to the server in order to verify it (because Apple recommends verifying from server rather than the app).
The receipt has symbols like, "+", "/", and "=". Since I could not send with those symbols I changed them, e.g. replacing + with "%2B" and so on.
But even after that I can get only a part of the receipt in my server. Sending it as a serialized Json also did not help.
(I need to send more data along with the receipt to the server, so that I cannot pass the receipt without converting into NSString)
How can I resolve this issue?