How to Retrieve User IP Addresses for reCAPTCHA Verification in App Engine Golang?

How to Retrieve User IP Addresses for CAPTCHA Verification in App Engine Golang

Introduction:
Integrating reCAPTCHA into web applications is essential for spam and fraud protection. To verify CAPTCHA solutions, obtaining the user's IP address is crucial. This article demonstrates how to fetch the IP address from form posts in Google App Engine (GAE) using Golang.

Retrieve User IP Address:
To obtain the user's IP address from a form post in GAE Golang, follow these steps:

1. Import the "net" package: import "net"
2. Use the r.RemoteAddr to access the client's network address: ip, _, _ := net.SplitHostPort(r.RemoteAddr)

The net.SplitHostPort function parses the client's network address, extracting the IP address (ip).

Code Example:

<code class="go">import "net"

func GetUserIP(r *http.Request) string {
    ip, _, _ := net.SplitHostPort(r.RemoteAddr)
    return ip
}</code>

Usage:

Once you have retrieved the IP address, you can use it to verify reCAPTCHA solutions as follows:

<code class="go">challenge := r.FormValue("g-recaptcha-response")
ip := GetUserIP(r)
resp, err := http.Get("https://www.google.com/recaptcha/api/siteverify?secret=" + recaptchaSecret + "&response=" + challenge + "&remoteip=" + ip)
// Validate reCAPTCHA response using retrieved IP and challenge</code>

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