能够访问一个服务来了解您的公共IP地址是非常有帮助的，但是这个过程是如何工作的呢？今天的超级用户问答帖子回答了一位好奇的读者的问题。

今天的问答环节是由SuperUser提供的，SuperUser是Stack Exchange的一个分支，是一个由社区驱动的问答网站分组。

截图由道格拉斯波特（Flickr）提供。

问题

超级用户读者Harry想知道查找计算机公共IP地址的步骤是：

I am aware of services like What Is My IP Address that allows a user to find their public IP address, but what I would like to know is how does such a service get written from scratch? I do not need the code itself, I just want to know the concepts and the steps involved (pseudo code if you will).

This is what I already know about creating such a service:

1. I would set up a web application on the Internet that listens to/for port 80.
2. When a request comes in, I would examine its source IP address and then package that in a nicely formatted HTML resp***e for the user to see.

Is that it, or is there something else involved here as well?

查找计算机的公共IP地址有哪些步骤？

答案

超级用户贡献者Scott Chamberlain为我们提供了答案：

For the most part, what you have listed is all that you need to do for basic functionality.

There is, however, one more thing you could do. You could check the X-Forwarded-For header added by some proxies (the kind used for caching) and/or load balancers and report that address instead because the address you get from the source address will be the proxy’s address, not the user’s.

However, that header is user provided, so there is no way to prove that the address listed in X-Forwarded-For is the real source address of the user.

有什么要补充的解释吗？在评论中发出声音。想从其他精通技术的Stack Exchange用户那里了解更多答案吗？在这里查看完整的讨论主题。