/* 06s.c */
#ifdef __cplusplus
#error Be sure you are using a C compiler...
#endif

#if defined (WIN32)
#include <winsock2.h>
#elif defined (linux)
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>             /* close */

#define INVALID_SOCKET -1
#define SOCKET_ERROR -1

#define closesocket(s) close (s)
typedef int SOCKET;
typedef struct sockaddr_in SOCKADDR_IN;
typedef struct sockaddr SOCKADDR;


#else
#error not defined for this platform
#endif

#include <stdio.h>
#include <stdlib.h>

/* macros ============================================================== */

#define TELNET 23

#define ESC 27

/* constants =========================================================== */
/* types =============================================================== */
/* structures ========================================================== */
/* private data ======================================================== */
/* private functions =================================================== */

/* ---------------------------------------------------------------------
   --------------------------------------------------------------------- */
static int app (void)
{
   int err = 0;

   /* open a socket in TCP/IP mode. */
   SOCKET sock = socket (AF_INET, SOCK_STREAM, 0);

   if (sock != INVALID_SOCKET)
   {
      printf ("socket %d is now opened in TCP/IP mode\n", sock);

      /* we want to listen on the TELNET port */
      {
         int sock_err;
         /* assign the listening port */
         SOCKADDR_IN sin =
         {0};

         /* automatic IP address */
         sin.sin_addr.s_addr = htonl (INADDR_ANY);

         /* protocol family (IP) */
         sin.sin_family = AF_INET;

         /* listening port */
         sin.sin_port = htons (TELNET);

         /* bind */
         sock_err = bind (sock, (SOCKADDR *) & sin, sizeof sin);

         if (sock_err != SOCKET_ERROR)
         {
            /* start listening (server mode) */
            sock_err = listen (sock, 5);

            printf ("listening on port %d...\n", TELNET);

            if (sock_err != SOCKET_ERROR)
            {
               /* wait for a client connection */
               printf ("waiting for a client connection on port %d...\n", TELNET);

               {
                  SOCKADDR_IN csin =
                  {0};
                  int recsize = (int) sizeof csin;
                  SOCKET csock = accept (sock, (SOCKADDR *) & csin, &recsize);

                  if (csock != INVALID_SOCKET)
                  {
                     printf ("client connected with socket %d from %s:%d\n"
                             ,csock
                             ,inet_ntoa (csin.sin_addr)
                             ,htons (csin.sin_port));
                     {
                        int end = 0;
                        do
                        {
                           /* wait for the receive of a data block (string expected, hence + 1) */
                           unsigned char data[128 + 1];
                           sock_err = recv (csock, data, (int) sizeof data - 1, 0);

                           if (sock_err != SOCKET_ERROR)
                           {
                              size_t nb_rec = (size_t) sock_err;
                              /* convert to string */
                              data[nb_rec] = 0;
                              printf ("%u byte%s received:\n%s\n"
                                      ,(unsigned) nb_rec
                                      ,nb_rec > 1 ? "s" : ""
                                      ,data);
                              fflush (stdout);

                              /* to be continued ... */
                              if (data[0] == ESC)
                              {
                                 end = 1;
                              }
                           }
                           else
                           {
                              perror ("socket.recv");
                              err = 1;
                              end = 1;
                           }
                        }
                        while (!end);
                     }
                     shutdown (csock, 2);
                     printf ("closing client socket %d...\n", csock);
                     closesocket (csock), csock = INVALID_SOCKET;

                  }
                  else
                  {
                     perror ("socket.accept");
                     err = 1;
                  }
               }
            }
            else
            {
               perror ("socket.listen");
               err = 1;
            }
         }
         else
         {
            perror ("socket.bind");
            err = 1;
         }

         printf ("closing socket %d...\n", sock);

         /* close the socket. */
         sock_err = closesocket (sock), sock = INVALID_SOCKET;

         printf ("the socket is now closed\n");

         if (sock_err)
         {
            perror ("socket.close");
            err = 1;
         }
      }
   }
   else
   {
      perror ("socket.open");
      err = 1;
   }

   return err;
}

/* entry point ========================================================= */

/* ---------------------------------------------------------------------
   --------------------------------------------------------------------- */
int main (void)
{
   int ret;
#if defined (WIN32)
   WSADATA wsa_data;
   int err = WSAStartup (MAKEWORD (2, 2), &wsa_data);

   if (!err)
   {
      puts ("WIN: winsock2: OK");
#else
   int err;
#endif

   err = app ();

#if defined (WIN32)
   WSACleanup ();
}
#endif

if (err)
{
   ret = EXIT_FAILURE;
}
else
{
   ret = EXIT_SUCCESS;
}
return ret;
}