update README.md

.gitignore

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+.DS_Store
+.idea/

README.md

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   <img alt="RenFeiBlog" src="./lib/assets/wordmark.light.png?raw=true" height="34">
 </picture></h1>
 
-My name is **RenFei(任霏)**, and I'm a Java programmer from China.
+My name is **RenFei(任霏)**, and I'm a Java programmer from Mainland China.
 
 ## Navigation
 
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 ### BT(BitTorrent) Tracker Service
 
 I run a public BitTorrent Tracker server: [http://tracker.renfei.net:8080/announce](http://tracker.renfei.net:8080/announce), which assists in communication between peers using the BitTorrent protocol, helps speed up BitTorrent downloads.
+
+### Internet IP Address Query Service
+
+Since the network may use multi-layer NAT address translation, IP address query for Internet egress:
+
+* [ip.renfei.net](http://ip.renfei.net) : IPv4 and IPv6, IPv6 is generally preferred, depending on the DNS resolution of the client.
+* [ipv4.renfei.net](http://ipv4.renfei.net) : IPv4 Only.
+* [ipv6.renfei.net](http://ipv6.renfei.net) : IPv6 Only.