#crc.py
def c(d,g):
    d+='0'*(len(g)-1)
    D,G=list(d),list(g)
    for i in range(len(D)-len(G)+1):
        if D[i]=='1':
            for j in range(len(G)):
                D[i+j]=str(int(D[i+j])^int(G[j]))
    return ''.join(D[-(len(G)-1):])

#server.py
import socket
from crc import c

s=socket.socket(socket.AF_INET,socket.SOCK_DGRAM)
s.bind(('localhost',6000))
print("Server listening on 6000...")

while True:
    data,addr=s.recvfrom(1024)
    m,cs=data.decode().split(',')
    if m.lower()=='exit':
        print("Client exit, shutting down.")
        break
    g=input("Enter generator (binary): ")
    cc=c(m+cs,g)
    print("Received message(CRC):",m+cs)
    print("Received checksum:",cs)
    print(f"Data from {addr} is {'valid' if all(i=='0' for i in cc) else 'invalid'}.")

s.close()

#client.py
import socket
from crc import c

while True:
    m=input("Enter message (binary) or 'exit': ")
    if m.lower()=='exit':
        with socket.socket(socket.AF_INET,socket.SOCK_DGRAM) as x:
            x.sendto("exit,exit".encode(),('localhost',6000))
        print("Exiting client.")
        break
    g=input("Enter generator (binary): ")
    cs=c(m,g)
    print("Checksum code:",cs)
    with socket.socket(socket.AF_INET,socket.SOCK_DGRAM) as x:
        x.sendto(f"{m},{cs}".encode(),('localhost',6000))