How to change the default port 3000 after creating a project with create-react-app?

The default port of the page that pops up after

1, npm install-g create-react-app
2, create-react-app my-app
3, cd my-app
4, npm start
is 3000. How to modify the default port? The server is not under the premise of this port number. Added:

to package.json

 "homepage": ".",
 "proxy":"http://localhost:8000",

Port create-react-app

Mar.02,2021

"proxy":"http://localhost:8000",

set the scripts "set PORT=3003&&react-app-rewired start" in package

windows environment "set PORT=3003&&react-app-rewired start"
mac environment "PORT=3003 react-app-rewired start"

Root directory to create a new .env.development file, add PORT=3001
, and 3001 is the port you want to change. Refer to " https://www.jianshu.com/p/195. "

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MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1b2bd46-40b09.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1b2bd46-40b09.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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