Using TCP Through Sockets

* Make file file descriptor nonblocking. */
if ((n = fcntl (s, F_GETFL)) < 0
|| fcntl (s, F_SETFL, n | O_NONBLOCK) < 0)
fatal ("O_NONBLOCK: %s\n", strerror (errno));
/* You can pretty much ignore the rest of this function... */
/* Many asynchronous programming errors occur only when slow peers
* trigger short writes. To simulate this during testing, we set
* the buffer size on the socket to 4 bytes. This will ensure that
* each read and write operation works on at most 4 bytes--a good
* stress test. */
#if SMALL_LIMITS
#if defined (SO_RCVBUF) && defined (SO_SNDBUF)
/* Make sure this really is a stream socket (like TCP). Code using
* datagram sockets will simply fail miserably if it can never
* transmit a packet larger than 4 bytes. */
{
int sn = sizeof (n);
if (getsockopt (s, SOL_SOCKET, SO_TYPE, (char *)&n, &sn) < 0
|| n != SOCK_STREAM)
return;
}
n = 4;
if (setsockopt (s, SOL_SOCKET, SO_RCVBUF, (void *)&n, sizeof (n)) < 0)
return;
if (setsockopt (s, SOL_SOCKET, SO_SNDBUF, (void *)&n, sizeof (n)) < 0)
fatal ("SO_SNDBUF: %s\n", strerror (errno));
#else /* !SO_RCVBUF || !SO_SNDBUF */
#error "Need SO_RCVBUF/SO_SNDBUF for SMALL_LIMITS"
#endif /* SO_RCVBUF && SO_SNDBUF */
#endif /* SMALL_LIMITS */
}
/* Enable keepalives to make sockets time out if servers go away. */
n = 1;
if (setsockopt (s, SOL_SOCKET, SO_KEEPALIVE, (void *) &n, sizeof (n)) < 0)
fatal ("SO_KEEPALIVE: %s\n", strerror (errno));
void *
xrealloc (void *p, size_t size)
{
p = realloc (p, size);
if (size && !p)
fatal ("out of memory\n");
return p;
}
void
fatal (const char *msg, ...)
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