[Q] Android and Arduino topic

Hey guys, I am new here, also i have never before developed for arduino. And my problem begins here, I tried to make a code that will send packs from android to arduino using DataGram but it didn't work, my app kept crashing, so I searched online and found a couple ready examples which kept crashing as well. From what I gather the problem comes from the use of android 4+ device.
Could you help or give me some example code to study and see whats wrong? Thanks a lot!