My PC has multiple IP addresses(ex: 10.1.1.20, 192.168.123.30, ...).

Can I extract the connected local ip address when connecting to remote server using http.Client?

If this is not possible with http.Client, is there any other possible way?

package main

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

func main() {
    req, err := http.NewRequest("GET", "https://www.google.com", nil)
    if err != nil {
        panic(err)
    }

    client := &http.Client{}
    resp, err := client.Do(req)
    if err != nil {
        panic(err)
    }
    defer resp.Body.Close()

    // extract the local ip address???
    // getsockname(?????)

    data, err := ioutil.ReadAll(resp.Body)
    if err != nil {
        panic(err)
    }

    fmt.Printf("StatusCode=%v\n", resp.StatusCode)
    fmt.Printf("%v\n", string(data))
}

CodePudding user response：

You can either:

• loop through all network interfaces
• or retrieve the preferred outbound ip address

But in both case, the fact that you are in the middle of using an http.Client and making a GET would not matter: you could get those IP addresses independently.

CodePudding user response：

You can provide your own Transport implementation that extracts the outgoing local IP address right after establishing the TCP connection, e.g. like this:

    client := &http.Client{
        Transport: &http.Transport{
            Dial: func(network, addr string) (net.Conn, error) {
                conn, err := net.Dial(network, addr)
                if err == nil {
                    localAddr := conn.LocalAddr().(*net.TCPAddr)
                    fmt.Println("LOCAL IP:", localAddr.IP)
                }

                return conn, err
            },
        },
    }