How to implement ip switching in golang

Golang implements ip switching

In network programming, IP address plays a vital role. However, in some special application scenarios, IP switching needs to be implemented. For example, some crawler programs, online games, etc. need to switch IP frequently to ensure the success of the operation. When implementing IP switching, golang can provide a simpler method.

1. Understanding IP address

In network programming, an IP address usually consists of 32 binary bits, usually written as four decimal numbers, with a Separated by ".", such as 192.168.100.1. Among them, the first three segments of the IP address represent the network number, and the last segment represents the host number.

2. Realize IP switching

IP switching can be achieved by calling the function under the net package in golang. First, you need to obtain the IP address of this machine. You can use the following code:

addrs, err := net.InterfaceAddrs()
if err != nil {
    log.Fatal(err)
}
for _, addr := range addrs {
    if ipnet, ok := addr.(*net.IPNet); ok && !ipnet.IP.IsLoopback() && ipnet.IP.To4() != nil {
        fmt.Printf("local ip address: %s\n", ipnet.IP.String())
    }
}

The above code obtains its IP address by traversing all network interfaces of this machine. Among them, ok means that the current IP address belongs to a net.IPNet type address and is not a loopback address. ipnet.IP.To4() != nil means that the returned IPv4 type address is.

Suppose we have a list of IP addresses, and you can select one of them through the following code:

var ips = []string{"192.168.0.101", "192.168.0.102", "192.168.0.103"}
conn, err := net.Dial("udp", "baidu.com:80")
if err != nil {
    log.Fatal(err)
}
localAddr := conn.LocalAddr().(*net.UDPAddr)
defer conn.Close()

var ip net.IP
for _, v := range ips {
    parsedIP := net.ParseIP(v)
    if parsedIP == nil { //无法将字符串转换为IPv4或IPv6地址
        continue
    }
    if localAddr.IP.Equal(parsedIP) {
        continue
    }
    ip = parsedIP
    break
}

In the above code, we first use the net.Dial function to dial a UDP connection, Then obtain the local IP address of the connection for easy selection in the IP list. We traverse the IP list, look for available IP addresses, and finally select an IP address that is different from the local IP to complete the IP address switch.

3. IP switching based on proxy

When crawling the target website, it is often necessary to implement IP switching through a proxy. Next, we explain how to use a proxy for IP switching.

First, you need to define a proxy type:

type Proxy struct {
    URL        string
    User       string
    Password   string
    DialerFunc func(network, address string) (net.Conn, error)
}

The proxy type includes proxy address (URL), proxy authentication (User, Password), and dial function. Among them, the parameters of the dial function are the network protocol (such as TCP, UDP) and the specified IP address, and it returns a network connection instance.

Based on this, we can use the following code to perform IP switching:

func main() {
    var proxy = Proxy{
        URL:        "http://60.205.200.130:80",
        User:       "",
        Password:   "",
        DialerFunc: func(network, address string) (conn net.Conn, e error) {
            return net.Dial("tcp", "60.205.200.130:80")
        },
    }

    transport := &http.Transport{
        Dial: proxy.DialerFunc,
    }

    client := &http.Client{
        Transport: transport,
    }

    res, err := client.Get("http://www.baidu.com")
    if err != nil {
        log.Fatal(err)
    }

    defer res.Body.Close()

    body, err := ioutil.ReadAll(res.Body)
    if err != nil {
        log.Fatal(err)
    }
    fmt.Println(string(body))
}

In the code, we first define a proxy type and define the DialerFunc function in it. In this function, We used the net.Dial function to connect to the network address 60.205.200.130:80 to establish a TCP connection. Next, we define an &http.Transport type instance and pass in the Dial function, which is used to respond to http requests. Finally, we define an &http.Client type instance and pass in the Transport instance, which is used to perform http requests.

Based on the above code, we can achieve the purpose of IP switching by switching proxy addresses multiple times.

Summary

This article mainly introduces the method of implementing IP switching in golang. By using the functions in the net package in golang, you can operate the IP address more easily. In the use of proxies, we can implement simulated requests for different IP addresses in applications such as web crawlers to meet the needs of application scenarios.

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