server.py

import sys
import re
import socket
import random
import getMac
import DHCP
from vlsm import *

Src = setserver()
if not Src :
    print("The given Server Cannot be configured")
    sys.exit(0)
print Src

MAX_BYTES = 65535
# Src = "192.168.1.1"
Dest = "255.255.255.255"
clientPort = 12345
serverPort = 12346

print("DHCP server is running.")
print("_________________________________________________")
dest = (Dest, serverPort)
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
sock.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)
sock.bind(('', clientPort))

Active = []
Offered = {}
while True :
    # Recieve messages
    data, address = sock.recvfrom(MAX_BYTES)
    # print("got something")
    try :
        TransactionId = DHCP.bytestring2hex(data[4:8],4)
    except Exception as e :
        print("Exception raised in TransactionId")
        print e,e.args
        continue
    MsgOptions = DHCP.ExtractOption(data)
    if not hex(53) in MsgOptions :
        continue

    if not TransactionId in Active :
        if MsgOptions[hex(53)][0]!= hex(1) :
            continue
        # DHCP Discover
        Active.append(TransactionId)
        ClientMacAddress = DHCP.bytestring2hex(data[28:34],6)
        Mac_str = []
        for i in range(6) :
            temp = ClientMacAddress[i][2:]
            temp = temp.upper()
            while len(temp) < 2 :
                temp = '0' + temp
            Mac_str.append(temp)

        Mac_str = ':'.join(Mac_str)
        print('\nGot DHCPDISCOVER : Transaction Id ' + str(TransactionId) + ' Mac  ' + Mac_str)

        # Get new Ip to be allocated to the client
        Check , Dic = getip(Mac_str)
        print Check
        print Dic
        OfferedIp = Dic['ClientIP'].split('.')
        SubnetMask = Dic['mask'].split('.')
        GateWayIp = Dic['GatewayIP'].split('.')
        DNSIp = Dic['DNSIP'].split('.')
        ServerIp = Src.split('.')

        OfferedIp = [ hex(int(OfferedIp[i])) for i in range(4) ]
        SubnetMask = [ hex(int(SubnetMask[i])) for i in range(4) ]
        GateWayIp = [ hex(int(GateWayIp[i])) for i in range(4) ]
        DNSIp = [ hex(int(DNSIp[i])) for i in range(4) ]
        ServerIp = [ hex(int(ServerIp[i])) for i in range(4) ]

        # DHCP Offer
        # If new Ip is not available
        if Check == 0 :
            print('\n DHCP Declined : Transaction Id ' + str(TransactionId) + ' Mac  ' + Mac_str)
            package = DHCP.DhcpDecline(ClientMacAddress,TransactionId,ServerIp)
            sock.sendto(package,dest)
            Active.remove(TransactionId)
            continue

        Offered[str(TransactionId)] = (ClientMacAddress,TransactionId,ServerIp,OfferedIp,SubnetMask,DNSIp,GateWayIp)
        package = DHCP.DhcpOffer(ClientMacAddress,TransactionId,ServerIp,OfferedIp,SubnetMask,DNSIp,GateWayIp)
        sock.sendto(package,dest)
        print('\n DHCP Offer : Transaction Id ' + str(TransactionId) + ' Offered Ip' + str(OfferedIp) )

    else :
        # DHCP Request
        if MsgOptions[hex(53)][0]!= hex(3) :
            continue
        print('\nGot DHCPREQUEST : Transaction Id ' + str(TransactionId) + ' Mac  ' + Mac_str)
        (ClientMacAddress,TransactionId,ServerIp,OfferedIp,SubnetMask,DNSIp,GateWayIp) = Offered[str(TransactionId)]

        # DHCP Ack
        package = DHCP.DhcpAck(ClientMacAddress,TransactionId,ServerIp,OfferedIp,SubnetMask,DNSIp,GateWayIp)
        sock.sendto(package,dest)
        print('\n DHCP Ack : Transaction Id ' + str(TransactionId) + ' Client Ip' + str(OfferedIp) )