Examples of DNS resolution

DNS.java

// javac DNS.java
// java DNS blah

import java.net.*;

public class DNS {
  public static void main(String[] args) {
    java.security.Security.setProperty("networkaddress.cache.ttl", "0");
    java.security.Security.setProperty("networkaddress.cache.negative.ttl", "0");

    for ( int i = 0 ; i < 1000 ; i++ ) {
      try {
        InetAddress address = InetAddress.getByName(args[0]);
        System.out.println(address.getHostAddress());
        Thread.sleep(1000);
      } catch ( UnknownHostException e ) {
        System.out.println(e);
        break;
      } catch ( InterruptedException e ) {
        System.out.println(e);
        break;
      }
    }
  }
}

dns.php

<?php
// php dns.php blah

$name = $argv[1];
for ( $i = 0 ; $i < 1000; $i++ )
{
  $ip = gethostbyname($name);
  print_r($ip."\n");
  sleep(1);
}

?>

dns2.php

<?php
// php dns2.php blah

$name = $argv[1];
for ( $i = 0 ; $i < 1000; $i++ )
{
  $ips = gethostbynamel($name);
  print_r(join(" ",$ips)."\n");
  sleep(1);
}

?>

getaddrinfo.c

// gcc -o getaddrinfo getaddrinfo.c
// ./getaddrinfo blah

#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <netdb.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>

int main(int argc, char *argv[])
{
  int i, j;
  struct hostent *he;
  struct in_addr **addr_list;

  if (argc != 2) {
      fprintf(stderr,"usage: %s hostname\n", argv[0]);
      return 1;
  }

  struct addrinfo hints, *servinfo, *p;
  int rv;

  memset(&hints, 0, sizeof hints);
  hints.ai_flags = AI_CANONNAME | AI_PASSIVE;
  hints.ai_family = AF_UNSPEC; // use AF_INET6 to force IPv6
  hints.ai_socktype = SOCK_STREAM;

  for ( i = 0 ; i < 1000 ; i++ )
  {
    if ((rv = getaddrinfo(argv[1], "http", &hints, &servinfo)) != 0) {
      fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
      return 1;
    }


    printf("%s: ", argv[1]);

    // loop through all the results and connect to the first we can
    for(p = servinfo; p != NULL; p = p->ai_next) {
      if ( p->ai_addr->sa_family == AF_INET ) {
        struct sockaddr_in *addr;
        addr =(struct sockaddr_in *)p->ai_addr;

        printf("%s ", inet_ntoa(addr->sin_addr));
      } else {
        printf("Not IPv4");
      }
    }

    printf("\n");
    sleep(1);
  }

  freeaddrinfo(servinfo); // all done with this structure
  return 0;
}

gethostbyname.c

// gcc -o gethostbyname gethostbyname.c
// ./gethostbyname blah

#include <stdio.h>
#include <errno.h>
#include <netdb.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>

int main(int argc, char *argv[])
{
    int i, j;
    struct hostent *he;
    struct in_addr **addr_list;

    if (argc != 2) {
        fprintf(stderr,"usage: %s hostname\n", argv[0]);
        return 1;
    }

    for ( i = 0 ; i < 1000 ; i++ )
    {
      if ((he = gethostbyname(argv[1])) == NULL) {  // get the host info
          herror("gethostbyname");
          return 2;
      }

      // print information about this host:
      printf("%s: ", he->h_name);
      addr_list = (struct in_addr **)he->h_addr_list;
      for(j = 0; addr_list[j] != NULL; j++) {
          printf("%s ", inet_ntoa(*addr_list[j]));
      }
      printf("\n");

      sleep(1);
    }

    return 0;
}

go-dns.go

package main
// go build go-dns.go
// ./go-dns blah

 import (
    "net"
    "flag"
    "fmt"
    "os"
    "time"
 )


func main() {
  flag.Parse()
  name := flag.Arg(0)

  for i := 0 ; i < 1000 ; i++ {
    ip, err := net.ResolveIPAddr("ip4", name)
    if err != nil {
      fmt.Println("Error:", err.Error())
      os.Exit(1)
    }

    fmt.Printf("%s: %s\n", name, ip.String())
    time.Sleep(1000 * time.Millisecond)
  }

  os.Exit(0)
}