sudo python3 main.py 172.16.16.181 2233 172.16.23.20 4444

custom_tcp_pkt.py

import socket
import struct
import array
import argparse

# Instantiate the parser
parser = argparse.ArgumentParser(description='Send custom tcp packet')

parser.add_argument('src_ip', type=str,
                    help='Source IP address')

parser.add_argument('src_port', type=int,
                    help='Source Port')

parser.add_argument('dst_ip', type=str,
                    help='Destination IP address')

parser.add_argument('dst_port', type=int,
                    help='Destination Port')
args = parser.parse_args()

class TCPPacket:
    def __init__(self,
                 src_host:  str,
                 src_port:  int,
                 dst_host:  str,
                 dst_port:  int,
                 flags:     int = 0):
        self.src_host = src_host
        self.src_port = src_port
        self.dst_host = dst_host
        self.dst_port = dst_port
        self.flags = flags
    def build(self) -> bytes:
        packet = struct.pack(
            '!HHIIBBHHH',
            self.src_port,  # Source Port
            self.dst_port,  # Destination Port
            0,              # Sequence Number
            0,              # Acknoledgement Number
            5 << 4,         # Data Offset
            self.flags,     # Flags
            8192,           # Window
            0,              # Checksum (initial value)
            0               # Urgent pointer
        )
        pseudo_hdr = struct.pack(
            '!4s4sHH',
            socket.inet_aton(self.src_host),    # Source Address
            socket.inet_aton(self.dst_host),    # Destination Address
            socket.IPPROTO_TCP,                 # PTCL
            len(packet)                         # TCP Length
        )
        checksum = self.chksum(pseudo_hdr + packet)
        packet = packet[:16] + struct.pack('H', checksum) + packet[18:]
        return packet

    def chksum(self, packet: bytes) -> int:
        if len(packet) % 2 != 0:
            packet += b'\0'

        res = sum(array.array("H", packet))
        res = (res >> 16) + (res & 0xffff)
        res += res >> 16

        return (~res) & 0xffff

pak = TCPPacket(
    args.src_ip,
    args.src_port,
    args.dst_ip,
    args.dst_port,
    0b000101001  # Merry Christmas!
)
s = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_TCP)
s.sendto(pak.build(), (args.dst_ip, 0))
BUFFER_SIZE = 10240
data = s.recv(BUFFER_SIZE)
s.close()

print ("received data:", data)