#include <sys/param.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/socket.h>

#include <netinet/in.h>

#include <err.h>
#include <errno.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#define SOBUF_SIZE	10000

#define PORT		23481

int
main(int argc, char **argv)
{
	struct sockaddr_in sin;
	int listenfd, connfd, pid, size, done, val, status, i;
	char buf[SOBUF_SIZE];
	char *data;

	if ((listenfd = socket(AF_INET, SOCK_STREAM, 0)) < 0)
		err(1, "socket error");

	val = SOBUF_SIZE;
	if (setsockopt(listenfd, SOL_SOCKET, SO_SNDBUF, &val,
		sizeof(val)) < 0)
		err(1, "setsockopt error");
	val = SOBUF_SIZE;
	if (setsockopt(listenfd, SOL_SOCKET, SO_RCVBUF, &val,
		sizeof(val)) < 0)
		err(1, "setsockopt error");

	memset(&sin, 0, sizeof(sin));
	sin.sin_family = AF_INET;
	sin.sin_port = htons(PORT);

	if (bind(listenfd, (struct sockaddr *) &sin,
		 sizeof(sin)) < 0)
		err(1, "bind error");

	if (listen(listenfd, 1024) < 0)
		err(1, "listen error");

	pid = fork();

	if (pid == -1)
		err(1, "fork error");

	if (pid != 0) {

		close(listenfd);
		sleep(1);

		if ((connfd = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
			(void)kill(pid, SIGTERM);
			err(1, "parent: socket error");
		}
		if (connect(connfd, (struct sockaddr *)&sin,
			    sizeof(sin)) < 0) {
			(void)kill(pid, SIGTERM);
			err(1, "parent: connect error");
		}


		for (i = 0; i < 2; i++) {
			data = buf;
			size = (i == 0 ? sizeof(buf) / 10 : sizeof(buf));

			printf("parent: sending %zu bytes...\n", size);
			do {
				printf("parent:   send(%zu)...\n", size);
				done = send(connfd, data, size, MSG_NOSIGNAL);
				if (done == 0) {
					break;
				} else if (done < 0) {
					(void)kill(pid, SIGTERM);
					err(1, "parent: send error");
				}
				printf("parent:   done(%zu).\n", done);
				data += done;
				size -= done;
			} while (size > 0);
			printf("parent: done.\n");
		}

		wait(&status);

		if (close(connfd) < 0) {
			(void)kill(pid, SIGTERM);
			err(1, "parent: close error");
		}


	} else {
		if ((connfd = accept(listenfd, (struct sockaddr *)NULL, NULL)) < 0)
			err(1, "child: accept error");

		sleep(5);

		for (i = 0; i < 2; i++) {

			size = (i == 0 ? sizeof(buf) / 10 : sizeof(buf));

			printf("child: recv(%zu, MSG_WAITALL)...\n", size);
			do {
				done = recv(connfd, buf, size, MSG_WAITALL);
			} while (done == -1 && errno == EINTR);
			if (done == 0)
				errx(1, "child: connection closed");
			else if (done < 0)
				err(1, "child: recv error");
			printf("child: done.\n");
		}

		if (close(connfd) < 0)
			err(1, "child: close error");
	}
	exit(0);
}