/* Byte Stream Connection Server Example

   Copyright (C) 1991-2018 Free Software Foundation, Inc.

   This program is free software; you can redistribute it and/or

   modify it under the terms of the GNU General Public License

   as published by the Free Software Foundation; either version 2

   of the License, or (at your option) any later version.

   This program is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License

   along with this program; if not, if not, see <http://www.gnu.org/licenses/>.

*/

#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	5555

#define MAXMSG	512

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);

		  }

	      }

	  }

    }

}