What is LLDB RPC Server ? When does it crash in Xcode? Why it crashes?

In my case: I update to Xcode Version 9.3 (9E145) recently and Xcode execute to the line with breakpoint then I type "po XXX" commend it will show the same message. I try to delete following files

~/Library/Preferences/com.apple.dt.Xcode.plist
~/Library/Caches/com.apple.dt.Xcode

and it solved. not knowing exactly why but worth to try.

remember to backup those files in order to recovered in case any unexpected situation occur.

I had the same problem and fixed it after I deleted some of the breakpoints. Not sure why this happen at all, but at least you can remove breakpoints and use some NSLog() or print() if you are in Swift and debug with the help of those. Good luck!

Make sure you are not running the app in release mode, if it is in release mode then change it to debug.

In my case the LLDB RPC server consistently crashed every time I ran my app, even after cleaning the build folder and removing and reinstalling Xcode (Version 8.3.3 (8E3004b)) completely.

It turned out that apparently LLDB took objection to a breakpoint I had set, just moving this breakpoint by a line resolved the issue.