//============================================== file = udpClientSelect.c =====
//=  A message "client" program to demonstrate sockets programming            =
//=   - This is udpClient.c modified to use select() as a timer               =
//=============================================================================
//=  Notes:                                                                   =
//=    1) This program conditionally compiles for Winsock and BSD sockets.    =
//=       Set the initial #define to WIN or BSD as appropriate.               =
//=    2) This program needs udpServer to be running on another host.         =
//=       Program udpServer must be started first.                            =
//=    3) This program assumes that the IP address of the host running        =
//=       udpServer is defined in "#define IP_ADDR"                           =
//=    4) To test this program (i.e., to demonstrate that the select() is     =
//=       working) the program will print "Time Out every 5 seconds if not    =
//=       receving anything from the server.                                  =
//=---------------------------------------------------------------------------=
//=  Example execution: (udpServer and udpClientSelect on host 127.0.0.1      =
//=                      with delay added in udpServer before sendto())       =
//=  Time out of recvfrom()...                                                =
//=  Time out of recvfrom()...                                                =
//=  Time out of recvfrom()...                                                =
//=  Time out of recvfrom()...                                                =
//=  Time out of recvfrom()...                                                =
//=  Time out of recvfrom()...                                                =
//=  Received from server: This is a reply message from SERVER to CLIENT      =
//=---------------------------------------------------------------------------=
//=  Build: bcc32 udpClientSelect.c or cl udpClientSelect.c wsock32.lib       =
//=         for Winsock, gcc udpClientSelect.c -lsocket -lnsl for BSD         =
//=---------------------------------------------------------------------------=
//=  Execute: udpClientSelect                                                 =
//=---------------------------------------------------------------------------=
//=  Author: Ken Christensen                                                  =
//=          University of South Florida                                      =
//=          WWW: http://www.csee.usf.edu/~christen                           =
//=          Email: christen@csee.usf.edu                                     =
//=---------------------------------------------------------------------------=
//=  History:  KJC (10/24/10) - Genesis (from udpClient.c)                    =
//=            BT  (09/21/14) - Made it to work for BSD                       =
//=            AA  (11/04/17) - Added select to simulate timeout              =
//=            KJC (11/05/14) - Minor clean-up                                =
//=            KJC (12/13/23) - Fix to select() for BSF (from Jo Embedded)    =
//=============================================================================
#define WIN               // WIN for Winsock and BSD for BSD sockets

//----- Include files ---------------------------------------------------------
#include <stdio.h>        // Needed for printf()
#include <string.h>       // Needed for memcpy() and strcpy()
#ifdef WIN
#include <windows.h>      // Needed for all Winsock stuff
#endif
#ifdef BSD
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>    // Needed for sockets stuff
#include <netinet/in.h>   // Needed for sockets stuff
#include <sys/socket.h>   // Needed for sockets stuff
#include <arpa/inet.h>    // Needed for sockets stuff
#include <fcntl.h>        // Needed for sockets stuff
#include <netdb.h>        // Needed for sockets stuff
#include <sys/select.h>   // Needed for select()
#endif

//----- Defines ---------------------------------------------------------------
#define  PORT_NUM           1050  // Port number used
#define  IP_ADDR      "127.0.0.1" // IP address of server (*** HARDWIRED ***)

//===== Main program ==========================================================
#ifdef WIN
void main(void)
#endif
#ifdef BSD
int main(void)
#endif
{
#ifdef WIN
  WORD wVersionRequested = MAKEWORD(1,1);       // Stuff for WSA functions
  WSADATA wsaData;                              // Stuff for WSA functions
#endif
  int                  client_s;      // Client socket descriptor
  unsigned long int    noBlock;       // Non-blocking flag
  struct sockaddr_in   server_addr;   // Server Internet address
  struct timeval       timeout;       // Struct for time interval for select()
  fd_set               recvsds;       // Recieve descriptor for select()
  int                  addr_len;      // Internet address length
  char                 out_buf[4096]; // Output buffer for data
  char                 in_buf[4096];  // Input buffer for data
  int                  retcode;       // Return code
  int                  s_socket;      // Retern code for select()

#ifdef WIN
  // This stuff initializes winsock
  WSAStartup(wVersionRequested, &wsaData);
#endif

  // Create a socket
  client_s = socket(AF_INET, SOCK_DGRAM, 0);
  if (client_s < 0)
  {
    printf("*** ERROR - socket() failed \n");
    exit(-1);
  }

  // Fill-in server socket's address information
  server_addr.sin_family = AF_INET;                 // Address family to use
  server_addr.sin_port = htons(PORT_NUM);           // Port num to use
  server_addr.sin_addr.s_addr = inet_addr(IP_ADDR); // IP address to use

  // Assign a message to buffer out_buf
  strcpy(out_buf, "Test message from CLIENT to SERVER");

  // Now send the message to server.
  retcode = sendto(client_s, out_buf, (strlen(out_buf) + 1), 0,
    (struct sockaddr *)&server_addr, sizeof(server_addr));
  if (retcode < 0)
  {
    printf("*** ERROR - sendto() failed \n");
    exit(-1);
  }

  // Uses select() to make the recvfrom() time out
  while (1)
  {
    // Clearing and setting the recieve descriptor
    FD_ZERO(&recvsds);
    FD_SET((unsigned int) client_s, &recvsds);

    // Setting the time interval to 1 second
    timeout.tv_sec = 1;
    timeout.tv_usec = 0;

    // Calling select()
#ifdef WIN
    s_socket = select(1, &recvsds, NULL, NULL, &timeout);
#endif
#ifdef BSD
    s_socket = select(client_s+1, &recvsds, NULL, NULL, &timeout);
#endif
    if (s_socket == 0)
    {
      printf("Time out of recvfrom()... \n");
    }
    else
    {
      addr_len = sizeof(server_addr);
      retcode = recvfrom(client_s, in_buf, sizeof(in_buf), 0,
        (struct sockaddr *)&server_addr, &addr_len);
      if (retcode < 0)
      {
        printf("*** ERROR - recvfrom() failed \n");
        exit(-1);
      }

      // Output the received message
      printf("Received from server: %s \n", in_buf);

      // Break out of the loop
      break;
    }
  }

  // Close all open sockets
#ifdef WIN
  retcode = closesocket(client_s);
  if (retcode < 0)
  {
    printf("*** ERROR - closesocket() failed \n");
    exit(-1);
  }
#endif
#ifdef BSD
  retcode = close(client_s);
  if (retcode < 0)
  {
    printf("*** ERROR - close() failed \n");
    exit(-1);
  }
#endif

#ifdef WIN
  // This stuff cleans-up winsock
  WSACleanup();
#endif
}