#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>

#define PORT    4444
#define MAXMSG  512

#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <netinet/in.h>

int make_socket(uint16_t port)
{
	int sock, val;
	struct sockaddr_in name;

	/* Create the socket. */
	sock = socket(PF_INET, SOCK_STREAM, 0);
	if (sock < 0) {
		perror("socket");
		exit(EXIT_FAILURE);
	}
	val = 1;
	setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val));

	/* Give the socket a name. */
	name.sin_family = AF_INET;
	name.sin_port = htons(port);
	name.sin_addr.s_addr = htonl(INADDR_ANY);
	if (bind(sock, (struct sockaddr *) &name, sizeof(name)) < 0) {
		perror("bind");
		exit(EXIT_FAILURE);
	}

	return sock;
}


int read_from_client(int filedes)
{
	char buffer[MAXMSG];
	int nbytes;

	nbytes = read(filedes, buffer, MAXMSG);
	if (nbytes < 0) {
		/* Read error. */
		perror("read");
		exit(EXIT_FAILURE);
	} else if (nbytes == 0)

		/* End-of-file. */
		return -1;
	else {
		/* Data read. */
		fprintf(stderr, "Server: got message: `%s'\n", buffer);
		return 0;
	}
}

int main(void)
{
	extern int make_socket(uint16_t port);
	int sock;
	fd_set active_fd_set, read_fd_set;
	int i;
	struct sockaddr_in clientname;
	size_t size;
	/* Create the socket and set it up to accept connections. */
	sock = make_socket(PORT);
	if (listen(sock, 1) < 0) {
		perror("listen");
		exit(EXIT_FAILURE);
	}

	/* Initialize the set of active sockets. */
	FD_ZERO(&active_fd_set);
	FD_SET(sock, &active_fd_set);

	while (1) {
		/* Block until input arrives on one or more active sockets. */
		read_fd_set = active_fd_set;
		if (select(FD_SETSIZE, &read_fd_set, NULL, NULL, NULL) < 0) {
			perror("select");
			exit(EXIT_FAILURE);
		}

		/* Service all the sockets with input pending. */
		for (i = 0; i < FD_SETSIZE; ++i)
			if (FD_ISSET(i, &read_fd_set)) {
				if (i == sock) {
					/* Connection request on original socket. */
					int new;
					size = sizeof(clientname);
					new = accept(sock,
						     (struct sockaddr *)
						     &clientname, &size);
					if (new < 0) {
						perror("accept");
						exit(EXIT_FAILURE);
					}
					fprintf(stderr,
						"Server: connect from host %s, port %hd.\n",
						inet_ntoa(clientname.
							  sin_addr),
						ntohs(clientname.
						      sin_port));
					FD_SET(new, &active_fd_set);
				} else {
					/* Data arriving on an already-connected socket. */
					if (read_from_client(i) < 0) {
						close(i);
						FD_CLR(i, &active_fd_set);
					}
				}
			}
	}
}