PKTSIZE
n = recv(peer, dp, PKTSIZE, 0);
static char buf[PKTSIZE];
static char ackbuf[PKTSIZE];
n = recvfrom(f, dp, PKTSIZE, 0,
char ackbuf[PKTSIZE];
char rbuf[PKTSIZE];
char buf[PKTSIZE]; /* room for data packet */