Changes are not normally needed. If you have issues with this file, or if it seems to change on its own, you maybe using "Simhub" as that can change the file via Simhubs, "Game configuartion" setting. The default game port is 9000 and default password is asd. If you have edited this file, iot may have been corrupted. 1 wrong space in the file, will make it fail. Do this to test your broadcasting.json file. Open "Notepad" and thge open C:\users\yourname\documents\assetto corsa competizione\config\broadcasting.json -->> click in the fgile and press Alt+A to select all the file text. Then go to this website -->> https://jsonlint.com/ then click inside the box and press Alt+V to paste the code into the box. Then click "Verify Json" This will confirm if your .json file is valid.
If you have trouble and just want to replace the json file, you can download it from here and extract the included broadcasting.json to c:\users\yourname\assetto corsa competizione\config folder and replace what is already there.