I don't know if it's my imagination but whenever my internet connection is down I can't run the simulator, is an internet connection queried?
If so, then what if I want to program (and run) offline for security reasons?
@powing not sure why your raising this issue on swift forum 
, but more importantly simulator not launching is not correlated to absence of network, unless and until some extremely weird modifications have been done in simulator itself. You can try old and tested formula of restarting the system and then check if that is useful in any way?
I think I have traced the issue back to my VPN, which blocks traffic when the internet is not working. There was an odd issue that if I didn't enable LAN sharing that I could not wirelessly run an app on a real device, and while that is enabled and I'm using the virtual simulator, when I had the internet off, but the VPN blocking all traffic, this interfered with the Simulator.
If I have the Wi-Fi off, but also the VPN software, then the Simulator works.