Golang : Convert IPv4 address to packed 32-bit binary format

There are times when we need to deal with low-level network functions such as dealing with C program and the IP version 4 string address format is not really suitable. The IP version 4 address needs to be converted to packed 32-bit binary format first.

For example,

IP address 127.0.0.1 packed to 7f000001

Below is an example on how to convert the IPv4 address to packed 32-bits with encoding/binary package.

Here you go!

 package main

 import (
 "bytes"
 "encoding/binary"
 "fmt"
 "math/big"
 "net"
 )

 func IP4toInt(IPv4Address net.IP) int64 {
 IPv4Int := big.NewInt(0)
 IPv4Int.SetBytes(IPv4Address.To4())
 return IPv4Int.Int64()
 }

 //similar to Python's socket.inet_aton() function
 //https://docs.python.org/3/library/socket.html#socket.inet_aton

 func Pack32BinaryIP4(ip4Address string) string {
 ipv4Decimal := IP4toInt(net.ParseIP(ip4Address))

 buf := new(bytes.Buffer)
 err := binary.Write(buf, binary.BigEndian, uint32(ipv4Decimal))

 if err != nil {
 fmt.Println("Unable to write to buffer:", err)
 }

 // present in hexadecimal format
 result := fmt.Sprintf("%x", buf.Bytes())
 return result
 }

 func main() {
 fmt.Println("IP address 127.0.0.1 packed to ", Pack32BinaryIP4("127.0.0.1"))
 fmt.Println("IP address 192.168.0.1 packed to ", Pack32BinaryIP4("192.168.0.1"))
 }

Output: