Q:

Xcode error connecting to simulator "Software caused connection abort"

When I try to run my project through the Xcode simulator, it keeps giving me the error "Software caused connection abort".
Tried restarting the simulator & Xcode, and I recently deleted the DerivedData folder as suggested in this post about broken playgrounds so that also didn't help.

A:

QUICK FIX
This is happening because you have multiple versions of Xcode installed. MacOS unfortunately only supports running one version of Xcode at a time, and it needs to know the location of the currently running version. To sort things out, choose one of the following: 
Quit all instances of Xcode and restart it
Try one of the other options below if that hasn't solved it.
Using the command line:

run   sudo xcode-select --switch /Applications/your_custom_folder_if_needed/Xcode.app
Restart your terminal and Xcode and it will work just fine.

No-command line users:

Quit all instances of Xcode
Start the instance of Xcode that you want to use
Go to Xcode -> Preferences -> Locations
Select the correct version in Command Line Tools
Done!

A:

It's due to multiple Xcode installed in your system. This is how you make it work:

Quit all running Xcodes
Re-launch Xcode
Go to Xcode > Preferences > Locations
Change to the correct version in Command Line Tools

Clean project and clear Derived data if necessary, then run!

A:

In my case quitting and re-launching given Xcode was enough. I had two Xcodes, stable and beta.

