When I run the server from my Samsung Galaxy Note 4 phone (stock/unrooted) and connect my wired USB gamepad to the Virtualhere Server running on my Windows 10 PC....it crashes and reboots my phone instantly when I open steam in big picture mode and the gamepad is in xinput mode. The gamepad says it is fully compatible from XP to windows 10 and can use the xbox 360 windows drivers if needed. If have the gamepaf in analog/directinput mode when I start Steam big picture it doesn't crash my phone. A few other gamepads like the logitech F310 and F71 wireless gamepad also seemed to crash my phone. I need to verify, but I think it happened when they connected and were switched to "xinput" mode also.
All the devices test and function on my note 4 and PC without virtualhere connecting them over the network.
I had no firewall and no anti-malware running at the time or since a previous boot up so I do not expect any issues from those kinds of things.
Unfortunately i cannot do much if it crashes your phone as its most definitively a bug in the android linux kernel. A userspace program like virtualhere should never crash the phones kernel (in theory). I assume when you say crash you mean the phone either locks entirely or reboots..
Anyway my advice is the upgrade to marshmallow android 6. Are you running that version?