#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <unistd.h>

int main(void)
{
	int s = socket(AF_INET, SOCK_STREAM, 0);
	if (s == -1)
	{
		return 1;
	}

	struct sockaddr_in addr;
	addr.sin_family = AF_INET;
	addr.sin_port = htons(80);
	addr.sin_addr.s_addr = INADDR_ANY;

	if (bind(s, (struct sockaddr*)&addr, sizeof(struct sockaddr_in)) == -1)
	{
		close(s);
		return 2;
	}

	if (listen(s, SOMAXCONN) == -1)
	{
		close(s);
		return 3;
	}

	char buf[1000];

	for (;;)
	{
		int c = accept(s, NULL, NULL);
		if (c == -1)
		{
			continue;
		}

		if (recv(c, buf, 1000, 0) <= 0)
		{
			close(c);
			continue;
		}

		else
		{
			if (send(c, "HTTP/1.1 200 OK\r\nContent-Length: 12\r\nConnection: close\r\nContent-Type: text/plain; charset=UTF-8\r\n\r\nHello world!", 111, 0) == -1)
			{
				close(c);
				continue;
			}
		}

		close(c);
	}

	close(s);

	return 0;
}