I am experimenting with Android's Wi-Fi Direct (or P2P if you prefer). I thought it was working very nicely between my two phones, but I realized I am encountering issues with the WifiP2pManager.discoverPeers() and/or WifiP2pManager.requestPeers(). I have observed these results:
No peers are discovered and no callbacks are fired for a good 1+ minute. I observe this through the Wi-Fi Direct portion of the Android Wi-Fi settings as well. This is odd because sometimes the discovery completes almost immediately.
I have a Roku device and phone B sitting next to phone A. While all are connected to my Wi-Fi, the Roku only appears ~10% of the time, while phones A and B appear to each other.
When I disconnected the two phones from all Wi-Fi and did another scan, the Roku showed up (!!!) but phone B did not until I had refreshed at least ten times.
My two phones are a Nexus 7 (running 4.4.4) and a Nexus 5 (running 5.0).
I was able to "solve" the problems of some phones not appearing by requesting peer discovery every 10 seconds. I think I was running into this because one phone was always the host and I didn't bother to have it discover peers (because it doesn't try to join them), and the Wifi Direct was going to sleep on the host phone. I don't do anything with the peer results, but it wakes up the Wifi Direct system. There's probably a better method to call but I'm not sure what it is. If I had to guess I'd say I'm wasting some battery life.