Python dhcp packet using raw socket

Question

I'm sending a DHCP Discover packet generated using python raw sockets but i didn't get a DHCP OFFER, I don't know what the problem is?

def DHCP(self):
    Op = '\x01'
    HwType = '\x01'
    HwAddrLen = '\x06'
    HopC = '\x00'
    TransactionID = self.TransactionID 
    NumOfSec = '\x00\x00'
    Flags_B_Res = '\x00\x00'
    ciaddr = '\x00\x00\x00\x00'
    yiaddr = '\x00\x00\x00\x00'
    siaddr = '\x00\x00\x00\x00'
    giaddr = '\x00\x00\x00\x00'
    chwaddr = self.macInBytes
    #chwaddr = '\xaa\x9f\xfa\xa4\x57\x9a'
    chwpadding = '\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
    srchostname = '\x00' * 64
    bootfilename = '\x00' * 128
    magic_cookie = '\x63\x82\x53\x63' # Taken from http://tools.ietf.org/html/rfc1497
    msg_type = '\x35\x01\x01'
    par_req_list = '\x37\x0d\x01\x1c\x02\x03\x0f\x06\x77\x0c\x2c\x2f\x1a\x79\x2a'
    end = '\xff'
    pkt =Op+HwType+HwAddrLen+HopC+TransactionID+NumOfSec+Flags_B_Res+ciaddr+yiaddr+siaddr+giaddr+chwaddr+chwpadding+srchostname+bootfilename+magic_cookie+msg_type+par_req_list+end

        return pkt

Note : I compared this packet with the dhclient(linux command) packet using wireshark and both packets were the same