Running test with appium on multiple devices using appium port & bootstrap port?

appium -a 192.168.0.103 -p 4723 --bootstrap-port 4730 -U --nodeconfig F:\Appium_allFiles\nodeconfig_2.json

appium -a 127.0.0.1 -p 4725 --bootstrap-port 4729 -U 192.168.157.102:5555 --nodeconfig %~dp0jsonFiles\nodeconfig_2.json

How to take port no's ? for the added devices ?

appium port no : 4723 & 4725 here 4723 is for first device appium service, but 4725 is an assumption or how else it has been declared ? bootstrap port no : 4730 & 4729