Receiving a part of packet via recvfrom (UDP)

I'm trying to receive a part of a packet via recvfrom. It actually works like this: ``` recvfrom(sockfd, serialised_meta, 12, flags, src_addr, addrlen); recvfrom(sockfd, serialised_buf, BUFLEN, flags, src_addr, addrlen); ``` The data is sent like this: ``` bufd->Serialise(serialised_buf, BUFLEN+12); sendto(sockfd, serialised_buf, BUFLEN+12, flags, dest_addr, addrlen); ``` So the idea is to read some meta data first and then decide whether to receive something else. The problem is that I receive 4 '/0' bytes in the beginning if second buffer (serialised_buf). It doesn't seem to be serialisation issue, I used my serialisation before, and everything was cool, while I was receiving the whole packet (meta and data) at once. Any ideas on how it could be fixed? PS. I understand I can just skip unnecessary bytes) But anyway, why it might be happening?