Generate TCP packet in python | Python raw socket | raw packet from IPv4 layer

Packet.py

import socket, sys
from struct import *
from random import randint
import time
import binascii

class IPv4:
	def __init__(self):
		pass
	def pack(self,srcip:str,destip:str):
		ihl = 5
		version = 4
		tos = 0
		tot_len = 20 + 20   # python seems to correctly fill the total length, dont know how ??
		id = 54321  #Id of this packet
		frag_off = 0
		ttl = 255
		protocol = 6
		check = 10  # python seems to correctly fill the checksum
		saddr = socket.inet_aton ( srcip )  #Spoof the source ip address if you want to
		daddr = socket.inet_aton ( destip )
		ihl_version = (version << 4) + ihl
		ip_header = pack('!BBHHHBBH4s4s' , ihl_version, tos, tot_len, id, frag_off, ttl, protocol, check, saddr, daddr)
		return ip_header
	def unpack(self,data:bytes):
		version_header_len = data[0]
		version = version_header_len >> 4
		header_len = (version_header_len & 15) * 4
		ttl, proto, src, target = struct.unpack('! 8x B B 2x 4s 4s', data[:20])
		return version, header_len, ttl, proto, ipv4(src), ipv4(target), data[header_len:]


class TCP:
	def __init__(self,ipv4=None):
		self.ipv4=ipv4
	def pack(self,srcport:int,destport:int,seq:int,ack_seq:int,fin:int=0,syn:int=0,rst:int=0,psh:int=0,ack:int=0,urg:int=0):
		# tcp header fields
		source = srcport   # source port
		dest = destport   # destination port

		doff = 5	#4 bit field, size of tcp header, 5 * 4 = 20 bytes

		window = socket.htons (5840)	#   maximum allowed window size
		check = 0
		urg_ptr = 0
		 
		offset_res = (doff << 4) + 0
		tcp_flags = fin + (syn << 1) + (rst << 2) + (psh <<3) + (ack << 4) + (urg << 5)
		 
		# the ! in the pack format string means network order
		tcp_header = pack('!HHLLBBHHH' , source, dest, seq, ack_seq, offset_res, tcp_flags,  window, check, urg_ptr)

		# pseudo header fields
		source_address = socket.inet_aton( source_ip )
		dest_address = socket.inet_aton(dest_ip)
		placeholder = 0
		protocol = 6
		tcp_length = len(tcp_header)
		print(tcp_length)
		 
		psh = pack('!4s4sBBH' , source_address , dest_address , placeholder , protocol , tcp_length);
		psh = psh + tcp_header;
		 
		tcp_checksum = self.checksums(psh)
		 
		# make the tcp header again and fill the correct checksum
		tcp_header = pack('!HHLLBBHHH' , source, dest, seq, ack_seq, offset_res, tcp_flags,  window, tcp_checksum , urg_ptr)
		if self.ipv4:
			return self.ipv4+tcp_header
		return tcp_header
	@staticmethod
	def checksums(msg):
		s = 0
		for i in range(0, len(msg), 2):
			w = (msg[i] << 8) + (msg[i+1])
			s = s + w
		s = (s>>16) + (s & 0xffff);
		s = ~s & 0xffff
		return s

send.py

'''
send tcp syn packet
'''
s = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_RAW)
# s = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_TCP)
s.setsockopt(socket.IPPROTO_IP, socket.IP_HDRINCL, 1)

source_ip = '192.168.0.243'
dest_ip = '35.170.21.246'
srcport= randint(2000,65535)
IPv4packet=IPv4().pack(srcip=source_ip,destip=dest_ip)

tcp=TCP(IPv4packet)
data={"srcport":srcport,"destport":80,"seq":0,"ack_seq":0,"syn":1,"rst":0,"psh":0,"ack":0}
packet=tcp.pack(**data)
s.sendto(packet, (dest_ip , 0 ))

'''
send tcp ack packet
'''
s = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_RAW)
# s = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_TCP)
s.setsockopt(socket.IPPROTO_IP, socket.IP_HDRINCL, 1)

source_ip = '192.168.0.243'
dest_ip = '35.170.21.246'
srcport= randint(2000,65535)
IPv4packet=IPv4().pack(srcip=source_ip,destip=dest_ip)

tcp=TCP(IPv4packet)
data={"srcport":srcport,"destport":80,"seq":1,"ack_seq":1,"syn":0,"rst":0,"psh":0,"ack":1}
packet=tcp.pack(**data)

s.sendto(packet, (dest_ip , 0 ))