This morning I ran into the same problem as you. I look into the Ionic input code (. \ Node_modules \ ionic \ lib \ ionic \ serve.js) and compare it with another file, I did not find the difference. So instead of using the grunt serve command, I tried the ion feed command. This script did not depend on the command line, so I could select the address. (in my case, I selected 2 (localhost)).
From this moment, it remembers the option you have selected. therefore, you can run the grunt serve command again.
If the ion feed command does not work, try installing ionic: "npm install -g ionic"
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