@Hootie81~~Thanks for your code and suggestion.
Use your new code under the hotspot connection, it always display timeout message just like it occupied at while loop before.
Then I use your new debug code to do many combination test to see what is the difference between WIFI and my iPhone hotspot connection.
Finally…I found the difference!!!. Just need to add one line client.println(); after the client.println(serverName); and then it will work well as WIFI network.
I do really thanks for your help, without your advise and code I can’t make it work in just one day. Thank you^^
But I am still confuse about why the behavior of hotspot is different from WIFI.