How to change IP address using perl (something like ipconfig release/renew)

Question

I am beginner to Perl and I have to write a script which could change the IP address after every 1 hour. I want to change it because I receive some data from a dongle from a website and that website has some time limit to receive that data, so currently we need to unplug the connecting device and use another to change IP address. (I mean I have to request DHCP for another IP.)

But currently I am asked to write a script using Perl. Could someone please help me how to do that?

My try to do it is :

#!/usr/bin/perl
# Simple DHCP client - sending a broadcasted DHCP Discover request

use IO::Socket::INET;
use Net::DHCP::Packet;
use Net::DHCP::Constants;

use POSIX qw(setsid strftime);

# sample logger
sub logger{
    my $str = shift;
    print STDOUT strftime "[%d/%b/%Y:%H:%M:%S] ", localtime;
    print STDOUT "$str\n";
}

logger("DHCPd tester - dummy client");

logger("Opening socket");
$handle = IO::Socket::INET->new(Proto => 'udp',
                                Broadcast => 1,
                                PeerPort => '67',
                                LocalPort => '68',
                                PeerAddr => '255.255.255.255',
                )
      || die "Socket creation error: $@\n";     # yes, it uses $@ here

# create DHCP Packet DISCOVER
$discover = Net::DHCP::Packet->new(
                      Xid => 0x12345678,
                      DHO_DHCP_MESSAGE_TYPE() => DHCPDISCOVER(),
                      DHO_VENDOR_CLASS_IDENTIFIER() => 'foo',
                      );
logger("Sending DISCOVER to 127.0.0.1:67");
logger($discover->toString());
$handle->send($discover->serialize())
              or die "Error sending:$!\n";

logger("Waiting for response from server");
$handle->recv($buf, 4096) || die("recv:$!");
logger("Got response");
$response = new Net::DHCP::Packet($buf);
logger($response->toString());

# create DHCP Packet REQUEST
$request = Net::DHCP::Packet->new(
                      Xid => 0x12345678,
                      Ciaddr => $response->yiaddr(),
                      DHO_DHCP_MESSAGE_TYPE() => DHCPREQUEST(),
                      DHO_VENDOR_CLASS_IDENTIFIER() => 'foo',
                      DHO_DHCP_REQUESTED_ADDRESS() => $response->yiaddr(),
                      );

logger("Sending REQUEST to 127.0.0.1:67");
logger($request->toString());

$handle->send($request->serialize())
              or die "Error sending:$!\n";
logger("Waiting for response from server");
$handle->recv($buf, 4096) || die("recv:$!");
logger("Got response");
$response = new Net::DHCP::Packet($buf);
logger($response->toString());

It's output on terminal is :

C:\shekhar_Axestrack_Intern\IpAddressChangeScripts>test6.pl
[08/Jan/2015:18:01:01] DHCPd tester - dummy client
[08/Jan/2015:18:01:01] Opening socket
[08/Jan/2015:18:01:01] Sending DISCOVER to 127.0.0.1:67
[08/Jan/2015:18:01:01] op = BOOTREQUEST
htype = HTYPE_ETHER
hlen = 6
hops = 0
xid = 12345678
secs = 0
flags = 0
ciaddr = 0.0.0.0
yiaddr = 0.0.0.0
siaddr = 0.0.0.0
giaddr = 0.0.0.0
chaddr =
sname =
file =
Options :
 DHO_DHCP_MESSAGE_TYPE(53) = DHCPDISCOVER
 DHO_VENDOR_CLASS_IDENTIFIER(60) = foo
padding [0] =

[08/Jan/2015:18:01:01] Waiting for response from server
//And it is stuck here since last 45 minutes....

My idea to do it is: I will send a request to server (DHCP) (I think DHCPREQUEST() do that)that please provide me new IP adress.

Could some one please let me know if my last line will print ID adress or not ? I mean :

$response = new Net::DHCP::Packet($buf);
logger($response->toString());

EDIT:

I also tried this on suggestion by the experienced guys below but it still do not change IP adress (even i tried to run this perl code 4 times without success in IP change-Even i tried to run manually ipconfig /renew but still the IP is same all the time).

my $ipconfig = `ipconfig /renew`;
my $ipcfg_success = $?;
print $ipconfig;
if ($ipcfg_success == 0) {
    do print "n succesfully runned \n";
} else {
    do "\n succesfully NOT sunned \n";
}

Answer 1

This more of a comment but it grew too long.

Just have your script call ipconfig /release and ipconfig /renew with a few seconds in between. That will request a new IP from the DHCP server, just as your script apparently tries to do.

Of course you are not exactly guaranteed a new IP that way, that depends on the configuration of the DHCP server but you are dependent on that either way. If the possible range of addresses is very small and you are afraid you might get the old IP by bad luck, check and renew again if it happened. If you get the same IP every time, it most likely means that the server recognizes you (by MAC or hostname) and assigns your static IP to you. In that case all you can do is talk to your network adminstrator (a course of action i would suggest anyways).

If you really need a guarantee, then you have to ditch DHCP and set your own IP. That however requires that you have some range of IPs reserved just for you. Otherwise your network administrator might hunt you down with their crossbow.

Be aware that depending on what that dongle is for and who set up that time limit, they may do anyways.

Answer 2

Writing a DHCP client isn't going to change your system's IP address. You need to use the system's client.

system('ipconfig /release & ipconfig /renew');

You're not guaranteed to get a new address, though. It causes less headaches if machines always have the same IP address, so DHCP servers tend to always give the same address to a machine.