Udp readfrom until the end

Socket Used : udp

I have a client who sends 5000 bytes and a server with this code :

Client code :

cod = sendto (sFd, (void *) buffer, 5000, 0, (struct sockaddr *)
            &soc, sizeof (struct sockaddr_in));

Server code :

//leghtBuffer = 5000
while (lenghtBuffer > 0 )
{
 //I will insert a signal if pass more than 30 s ...
 cod = recvfrom (sFd, buffer,256 , 0, (struct sockaddr *) &clientSoc, &lungimeSocket); 

 printf("Am received %d bytes " ,cod );
 lenghtBuffer = lenghtBuffer - cod;

}

How can I read more than 1 time 256 bytes from this while (still using Udp socket)?