#define _POSIX_SOURCE
#define _BSD_SOURCE

#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <netdb.h>

/*
 * server.c: Implementation of a very simple tcp server.
 */
int main(int argc, char *argv[])
{
	struct addrinfo hints;	/* specify our needs */
	struct addrinfo *res;	/* resulting address structure */
	struct addrinfo *r;	/* iterator */
	int err;		/* status of get{addr,name}info() */
	int ss;			/* the server's socket */
	int cs;			/* the client's socket */
	ssize_t read;		/* received bytes */
	char c;			/* used to store received byte */

	struct sockaddr sa;     /*********************/
	socklen_t len;          /* $ man getnameinfo */
	char hbuf[NI_MAXHOST];  /*********************/

	/* Enforce correct usage */
	if (argc != 2)
	{
		printf("Usage: %s [port]\n", argv[0]);
		exit(EXIT_FAILURE);
	}

	memset(&hints, 0, sizeof(hints));
	hints.ai_family = AF_INET;		/* IPv4 */
	hints.ai_socktype = SOCK_STREAM;	/* Stream socket */
	hints.ai_flags = AI_PASSIVE;		/* INADDR_ANY */
	hints.ai_protocol = 0;			/* Any (TCP) */

	/*
		$ man getaddrinfo
		[...]
		Given node and service, which identify an Internet host and a
		service, getaddrinfo() returns one or more addrinfo structures,
		each of which contains an Internet address that can be specified
		in a call to bind(2) or connect(2).
		[...]
	*/
	err = getaddrinfo(NULL, argv[1], &hints, &res);
	if (err != 0)
	{
		fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(err));
		exit(EXIT_FAILURE);
	}

	/* Loop through the address structures */
	for (r = res; r != NULL; r = r->ai_next)
	{
		/* Create the socket */
		ss = socket(res->ai_family, res->ai_socktype, res->ai_protocol);

		if (ss < 0)
		{
			perror("socket");
			continue;
		}

		/* Bind the address to the socket */
		if (bind(ss, res->ai_addr, res->ai_addrlen) < 0)
		{
			close(ss);
			perror("bind");
			continue;
		}

		break;	/* Success*/
	}

	/* Give up */
	if (r == NULL)
	{
		fprintf(stderr, "Binding failed!\n");
		exit(EXIT_FAILURE);
	}

	/* No longer needed */
	freeaddrinfo(res);

	/* Listen for incoming connections */
	if (listen(ss, 0) < 0)
	{
		perror("listen");
		exit(EXIT_FAILURE);
	}

	printf("Waiting...\n");

	/*
		$ man accept
		[...]
		The addrlen argument is a value-result argument: the
		caller must initialize it to contain the size
		(in bytes) of the structure pointed to by addr; on
		return it will contain the actual size of the peer
		address.
		[...]
	*/
	len = sizeof(sa);

	/* Wait for and accept new connection */
	cs = accept(ss, &sa, &len);
	if (cs < 0)
	{
		perror("accept");
		exit(EXIT_FAILURE);
	}

	/* Lookup client's hostname */
	err = getnameinfo(&sa, len, hbuf, sizeof(hbuf), NULL, 0, 0);
	if (err != 0)
	{
		fprintf(stderr, "getnameinfo: %s\n", gai_strerror(err));
		/* Print the error, but do not exit */
	}

	printf("Connection established...\n");
	printf("-------------------------\n");
	printf("%s:\n\n", hbuf);

	/* Infiniteley reading characters */
	for (;;)
	{
		/* Finally: Receive user's message */
		read = recv(cs, &c, 1, 0);
		if (read > 0)
		{
			printf("%c", c);
			fflush(stdout);
		}
		else
		{
			/*
				$ man recv
				[...]
				These calls return the number of bytes received,
				or -1 if an error occurred. The return value
				will be 0 when the peer has performed an orderly
				shutdown.
				[...]
			*/
			if (read < 0)
			{
				perror("recv");
			}
			else /* read == 0 */
			{
				printf("\n-------------------\n");
				printf("Orderly shutdown...\n");
			}

			close(cs);
			break;
		}
	}

	/* Clean up */
	close(ss);

	return EXIT_SUCCESS;
}