Xcode 9 beta builds project but fails to launch simulator.

I've got XCode 9 beta building my project but then I get an alert: "Error returned in reply: Connection Invalid - Software caused connection abort"

Launching the simulator from the tools menu shows the frame with the Apple logo as if it's booting.

Trying to change devices in the simulator gives "Error returned in reply: Connection invalid".

I still have XCode 8 installed but have tried rebooting and launching directly into beta 9 with the same results.


Same here, so I've not been able to do anything with Xcode 9. Did you happen upon a solution yet?

I had this problem too, but after rebooting the machine, connecting an iPhone, running it on the iPhone and then trying it on the Simulator again did the trick. (Not sure what resolved it, but some of these things helped.)

You have both Xcode 8.x.x and 9 running on your Mac, which causes the problem. Only run one Xcode at a time (Quit another Xcode, don't let another Xcode runing in background!).

Same question with other solutions here: https://forums.developer.apple.com/message/233868#233868

you can reopen you Xcode9 , i alse meet that problem just now.

The same rules as in the past apply to switching between Xcode 8 and Xcode 9:

1. Quit Xcode, Instruments, Simulator.app, and Console

2. xcode-select the version you want to work with

3. Start the version of Xcode you want to use

There is a known bug with macOS Sierra 10.12.5 where opening Console will forcibly start Xcode 9's CoreSimulator service. Upgrading to 10.12.6 or macOS High Sierra resolves the problem.

If these steps don't resolve the problem for you you can repeat the steps above but after #2 add "sudo killall -9 com.apple.CoreSimulator.CoreSimulatorService". This shouldn't be necessary, so please file a radar and let us know if this happens to you and how you resolved it.

I got it running after quiting and reopening xcode

Closing Xcode, Console and Simulator resolved the error for me.