How to prevent iPhone from dropping wifi connection when it goes to sleep? I am using whatsapp web version and the iPhone needs to be connected at all times for it to work. However, when the iPhone goes to sleep (screen goes off) the wifi connected is automatically turned off to save battery and the whatsapp on my browser disconnects. Is there a way to force iPhone to keep wifi connection up when locked and/or asleep?
I have the same iPhone and the same problem. I just went into Settings > General > Reset > Reset Network Settings. Then reconnect to your wifi like normal. 

This worked for me, however if the problem is still there, maybe turn your data off when using wifi. Hope one method works for you (: