manual/examples/inetsrv.c

   1 #include <stdio.h>
   2 #include <errno.h>
   3 #include <stdlib.h>
   4 #include <unistd.h>
   5 #include <sys/types.h>
   6 #include <sys/socket.h>
   7 #include <netinet/in.h>
   8 #include <netdb.h>
   9
  10 #define PORT    5555
  11 #define MAXMSG  512
  12
  13 int
  14 read_from_client (int filedes)
  15 {
  16   char buffer[MAXMSG];
  17   int nbytes;
  18
  19   nbytes = read (filedes, buffer, MAXMSG);
  20   if (nbytes < 0)
  21     {
  22       /* Read error. */
  23       perror ("read");
  24       exit (EXIT_FAILURE);
  25     }
  26   else if (nbytes == 0)
  27     /* End-of-file. */
  28     return -1;
  29   else
  30     {
  31       /* Data read. */
  32       fprintf (stderr, "Server: got message: `%s'\n", buffer);
  33       return 0;
  34     }
  35 }
  36
  37 int
  38 main (void)
  39 {
  40   extern int make_socket (unsigned short int port);
  41   int sock;
  42   fd_set active_fd_set, read_fd_set;
  43   int i;
  44   struct sockaddr_in clientname;
  45   size_t size;
  46
  47   /* Create the socket and set it up to accept connections. */
  48   sock = make_socket (PORT);
  49   if (listen (sock, 1) < 0)
  50     {
  51       perror ("listen");
  52       exit (EXIT_FAILURE);
  53     }
  54
  55   /* Initialize the set of active sockets. */
  56   FD_ZERO (&active_fd_set);
  57   FD_SET (sock, &active_fd_set);
  58
  59   while (1)
  60     {
  61       /* Block until input arrives on one or more active sockets. */
  62       read_fd_set = active_fd_set;
  63       if (select (FD_SETSIZE, &read_fd_set, NULL, NULL, NULL) < 0)
  64         {
  65           perror ("select");
  66           exit (EXIT_FAILURE);
  67         }
  68
  69       /* Service all the sockets with input pending. */
  70       for (i = 0; i < FD_SETSIZE; ++i)
  71         if (FD_ISSET (i, &read_fd_set))
  72           {
  73             if (i == sock)
  74               {
  75                 /* Connection request on original socket. */
  76                 int new;
  77                 size = sizeof (clientname);
  78                 new = accept (sock,
  79                               (struct sockaddr *) &clientname,
  80                               &size);
  81                 if (new < 0)
  82                   {
  83                     perror ("accept");
  84                     exit (EXIT_FAILURE);
  85                   }
  86                 fprintf (stderr,
  87                          "Server: connect from host %s, port %hd.\n",
  88                          inet_ntoa (clientname.sin_addr),
  89                          ntohs (clientname.sin_port));
  90                 FD_SET (new, &active_fd_set);
  91               }
  92             else
  93               {
  94                 /* Data arriving on an already-connected socket. */
  95                 if (read_from_client (i) < 0)
  96                   {
  97                     close (i);
  98                     FD_CLR (i, &active_fd_set);
  99                   }
 100               }
 101           }
 102     }
 103 }