使用 python scapy 发送 DHCP Discover

I am new to python and learning some network programming, I wish to send an DHCP Packet through my tap interface to my DHCP server and expecting some response from it. I tried with several packet building techniques such a structs and ctypes and ended up with using scapy. Here I am able to send DHCP Packet but unable to get any response from the DHCP server(Analyzed using wireshark and tcpdump)..My packet looked like same as original DHCP packet but failed to get response. Here is my code

import socket
from scapy.all import *

def main():

 if len(sys.argv)<3:
   print " fewer arguments."
   sys.exit(1)
 else:
   tap_interface = sys.argv[1]
   src_mac_address = sys.argv[2]

 ethernet = Ether(dst='ff:ff:ff:ff:ff:ff',src=src_mac_address,type=0x800)
 ip = IP(src ='0.0.0.0',dst='255.255.255.255')
 udp =UDP (sport=68,dport=67)
 fam,hw = get_if_raw_hwaddr(tap_interface)
 bootp = BOOTP(chaddr = hw, ciaddr = '0.0.0.0',xid =  0x01020304,flags= 1)
 dhcp = DHCP(options=[("message-type","discover"),"end"])
 packet = ethernet / ip / udp / bootp / dhcp

 fd = open('/dev/net/tun','r+')
 TUNSETIFF = 0x400454ca
 IFF_TAP = 0x0002
 IFF_NO_PI = 0x1000
 mode = IFF_TAP | IFF_NO_PI
 ifr = struct.pack('16sH', tap_interface, IFF_TAP | IFF_NO_PI)
 fcntl.ioctl(fd,TUNSETIFF,ifr)


 while True:
    sendp(packet, iface = tap_interface)
    time.sleep(10)


 if __name__ == '__main__':
     main()

还有其他方法可以实现吗?如果是这样，请务必提及它们.提前致谢.