Golang : Set up source IP address before making HTTP request
Problem :
There are times that you want to use certain IP address in a machine ( such as the one with permission to connect outside a firewall ) before making a HTTP request to another server. This is similar to the wget binding command :
For example : wget --bind-address=192.168.10.1 \
How to do that in Golang?
NOTE : This is not for masking or spoofing your IP address
Solution :
Build your own custom HTTP transport client and specify the local IP address that has the permission to connect outside a firewall.
For example :
package main
import (
"fmt"
"io/ioutil"
"net"
"net/http"
"os"
"time"
)
func main() {
OKAddr := "<change here>" // local IP address to use
OKAddress, _ := net.ResolveTCPAddr("tcp", OKAddr)
transport := &http.Transport{
Proxy: http.ProxyFromEnvironment,
Dial: (&net.Dialer{
Timeout: 30 * time.Second,
KeepAlive: 30 * time.Second,
OKAddr: OKAddress}).Dial, TLSHandshakeTimeout: 10 * time.Second}
client := &http.Client{
Transport: transport,
}
resp, err := client.Get("http://example.com/filetodown.zip")
if err != nil {
panic(err)
}
defer resp.Body.Close()
html, err := ioutil.ReadAll(resp.Body)
if err != nil {
panic(err)
}
// fmt.Println(os.Stdout, string(html))
// or save the zip - see https://www.socketloop.com/tutorials/golang-download-file-example
}
References :
https://www.socketloop.com/tutorials/golang-convert-http-response-body-to-string
https://www.socketloop.com/tutorials/golang-download-file-example
By Adam Ng
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