//====================================================== file = server1.c ====
//=  A message "server" program to demonstrate sockets programming           =
//=   - UDP/IP client/server model is implemented                            =
//============================================================================
//=  Notes:                                                                  =
//=    1) This program conditionally compiles for Winsock and BSD sockets.   =
//=       Set the initial #define to WIN or BSD as appropriate.              =
//=    2) There is *no* error checking in this program.  Error checking was  =
//=       omitted to simplify the program.                                   =
//=    3) This program serves a message to program client1 running on        =
//=       another host.                                                      =
//=    4) This program assumes that the client1 has the IP address hardcoded =
//=       into "#define IP_ADDR"                                             =
//=    5) The steps #'s correspond to lecture topics.                        =
//=--------------------------------------------------------------------------=
//=  Build: bcc32 UDPServer.c or cl server1.c wsock32.lib for Winsock          =
//=         gcc server1.c -lsocket -lnsl for BSD                             =
//=--------------------------------------------------------------------------=
//=  History:  KJC (03/02/99) - Genesis (from server.c)                      =
//============================================================================
#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 <sys/types.h>    // Needed for system defined identifiers.
  #include <netinet/in.h>   // Needed for internet address structure.
  #include <sys/socket.h>   // Needed for socket(), bind(), etc...
  #include <arpa/inet.h>    // Needed for inet_ntoa()
  #include <fcntl.h>        // Needed for sockets stuff
  #include <netdb.h>        // Needed for sockets stuff
#endif

//----- Defines -------------------------------------------------------------
#define  PORT_NUM           1050  // Port number used
#define  IP_ADDR "127.0.0.1" // IP address of server1 (*** HARDWIRED ***)

//===== Main program ========================================================
void main(void)
{
#ifdef WIN
  WORD wVersionRequested = MAKEWORD(1,1);       // Stuff for WSA functions
  WSADATA wsaData;                              // Stuff for WSA functions
#endif

  unsigned int         server_s;        // Server socket descriptor
  struct sockaddr_in   server_addr;     // Server1 Internet address
  struct sockaddr_in   client_addr;     // Client1 Internet address
  int                  addr_len;        // Internet address length
  char                 out_buf[100];    // 100-byte buffer for output data
  char                 in_buf[100];     // 100-byte buffer for input data
  long int             i;               // Loop counter

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

  // >>> Step #1 <<<
  // Create a socket
  //   - AF_INET is Address Family Internet and SOCK_DGRAM is datagram
  server_s = socket(AF_INET, SOCK_DGRAM, 0);

  // >>> Step #2 <<<
  // Fill-in my socket's address information
  server_addr.sin_family      = AF_INET;            // Address family to use
  server_addr.sin_port        = htons(PORT_NUM);    // Port number to use
  server_addr.sin_addr.s_addr = htonl(INADDR_ANY);  // Listen on any IP address
  bind(server_s, (struct sockaddr *)&server_addr, sizeof(server_addr));

  // >>> Step #3 <<<
  // Fill-in client1 socket's address information
  client_addr.sin_family      = AF_INET;            // Address family to use
  client_addr.sin_port        = htons(PORT_NUM);    // Port num to use
  client_addr.sin_addr.s_addr = inet_addr(IP_ADDR); // IP address to use

  // >>> Step #4 <<<
  // Wait to receive a message from client1
  addr_len = sizeof(client_addr);
  recvfrom(server_s, in_buf, sizeof(in_buf), 0,
    (struct sockaddr *)&client_addr, &addr_len);

  // Output the received message
  printf("Message received is: '%s' \n", in_buf);

  // Assign a message to buffer out_buf
  strcpy(out_buf, "Reply message from server1 to client1");

  // >>> Step #5 <<<
  // Now send the message to client1.  The "+ 1" is for the end-of-string
  // delimiter
  sendto(server_s, out_buf, (strlen(out_buf) + 1), 0,
    (struct sockaddr *)&client_addr, sizeof(client_addr));

  // >>> Step #6 <<<
  // Close all open sockets
#ifdef WIN
  closesocket(server_s);
#endif
#ifdef BSD
  close(server_s);
#endif
#ifdef WIN
  // This stuff cleans-up winsock
  WSACleanup();
#endif
}