Golang : Find network of an IP address

We will learn how to use Golang's net package to find out the network behind an IP address. It is fairly trivial to do so with Go and below is the source code.

findnetwork.go

 package main

 import (
 "fmt"
 "net"
 "os"
 )

 func main() {
 if len(os.Args) != 2 {
 fmt.Fprintf(os.Stderr, "Usage: %s hostname\n", os.Args[0])
 os.Exit(1)
 }

 hostname := os.Args[1]

 IPAddr, err := net.ResolveIPAddr("ip", hostname)
 if err != nil {
 fmt.Println("Error in resolving IP")
 os.Exit(1)
 }


 addr := net.ParseIP(IPAddr.String())

 if addr == nil {
 fmt.Println("Invalid address")
 os.Exit(1)
 }
 mask := addr.DefaultMask()
 network := addr.Mask(mask)

 fmt.Printf("Address : %s \n Network : %s \n", addr.String(), network.String())
 }

Sample output :

localhost:~ admin$ ./findnetwork www.nytimes.com

Address : 170.149.172.130

Network : 170.149.0.0

localhost:~ admin$ ./findnetwork www.techcrunch.com

Address : 192.0.83.250

Network : 192.0.83.0

localhost:~ admin$ ./findnetwork www.google.com

Address : 74.125.130.104

Network : 74.0.0.0

localhost:~ admin$ ./findnetwork www.yahoo.com

Address : 106.10.139.246

Network : 106.0.0.0

Reference :

http://golang.org/pkg/net/#ParseIP

http://golang.org/pkg/net/#DefaultMask