@wchen-r7  Not sure if it's reliable enough to be hardcoded.   Initially I used ifconfig.me/ip but I found that icanhazip.com is much more faster. It's been up a couple of years. If you want I can set an OptString with a default resolver value. Another option is to put several services like these in a list and set a timeout. If I get no reponse in X seconds I use the next one. 
Let me know what you think is best.