Get client IP Address in Go

Knowing who is accessing your web server can be useful for tracking a user's activity. In this tutorial, we will learn how to get client IP address in Go.

To get the IP address of a client, just use

 ip,_,_ := net.SplitHostPort(r.RemoteAddr)

However, sometimes the user access your web server via a proxy or load balancer ( such as in cloud hosting etc ) and the above code will give you the IP address of the proxy or load balancer.

To get the real IP address of the client, you can get the HTTP Request header information "X-Forwarded-For (XFF)"

 fmt.Fprintf(w,"X-Forwarded-For :" + r.Header.Get("X-FORWARDED-FOR"));

This is the full code example that you can execute in your web server and test out with your web browser or curl.

client_ip.go

 package main

 import (
  "fmt"
  "net/http"
  "net"
 )

 func IndexPage(w http.ResponseWriter, r *http.Request) {
  // get client ip address
  ip,_,_ := net.SplitHostPort(r.RemoteAddr)


  // print out the ip address
  fmt.Fprintf(w,ip + "\n\n")

  // sometimes, the user acccess the web server via a proxy or load balancer.
  // The above IP address will be the IP address of the proxy or load balancer and not the user's machine.


  // let's get the request HTTP header "X-Forwarded-For (XFF)"
  // if the value returned is not null, then this is the real IP address of the user.
  fmt.Fprintf(w,"X-Forwarded-For :" + r.Header.Get("X-FORWARDED-FOR"));
 }


 func main() {
  http.HandleFunc("/", IndexPage)
  http.ListenAndServe(":8080", nil)
 }

References:

http package

Google App Engine Golang - how to get user's IP address?

Using "X-Forwarded-For" in Apache or PHP