/* 
 * Example of server using UDP protocol.
 */

#include "inet.h"
#include <signal.h>
#include <fcntl.h>
int sigflag = 0;      // sigflag == 1 if an I/O occurs

int main(int argc,char *argv[])
{
   int                sockfd;
   struct sockaddr_in serv_addr;
   void serv_act(int sockfd);

   /* 
    * Open a UDP socket (an Internet datagram socket)
    */

   if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
       err_dump("server: can't open datagram socket");

   /* 
    * Bind our local address so that the client can send to us.
    */
  
   bzero((char *)&serv_addr, sizeof(serv_addr));
   serv_addr.sin_family = AF_INET;
   serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
   serv_addr.sin_port = htons(SERV_UDP_PORT);

   if (bind(sockfd, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0)
      err_dump("server: can't bind local address");

   serv_act(sockfd);
   
   return 0;
}

/*
 * Read a datagram from a connectionless socket and write it back to
 * the sender.
 */

#define MAXMESG 2048

void serv_act(int sockfd)
{
   struct sockaddr *pcli_addr;
   struct hostent *host_info;
   int maxclilen;
   int  n, clilen;
   int client_port = -1;
   char mesg[MAXMESG];
   void sigio_func();        // signal handler
   void process();          // user application
   int i;

   pcli_addr = new (struct sockaddr);
   maxclilen = sizeof(struct sockaddr);
   host_info = new (struct hostent);

   /* interrupt handler */
   /* signal(SIGIO,sigio_func);
    */

   /* 
    * set up the socket so it is non-blocking
    */
   /*
   if (fcntl(sockfd, F_SETOWN, getpid()) < 0)
      err_dump("F_SETOWN error");
   if (fcntl(sockfd, F_SETFL, FASYNC) < 0)
      err_dump("F_SETFL FASYNC error");   

   for ( ; ; )
   {
     while (sigflag == 0)
        process();

   */
   while (1)
   {
     clilen = maxclilen;
     n = recvfrom(sockfd, mesg, MAXMESG, 0, pcli_addr, (socklen_t*)&clilen);
     if (n < 0)
          err_dump("dg_echo: recvfrom error");

     host_info = gethostbyaddr((char *)&(((struct sockaddr_in
					   *)pcli_addr)->sin_addr.s_addr),
			       sizeof (struct in_addr), AF_INET);

     client_port = ((struct sockaddr_in *)pcli_addr)->sin_port;
     printf(" client port  number : %d\n", client_port);
     if (host_info != NULL)
     {
	 printf(" hostname %s\n",host_info->h_name);

	 /* print all aliases */
	 char *ptr;
	 while ((ptr = *(host_info->h_aliases)) != NULL)
	 {
	     printf(" alias: %s\n", ptr);
	     host_info->h_aliases ++;
	 }
	 printf("   addr type = %d, addr length = %d\n",
		host_info->h_addrtype, host_info->h_length);

	 /* print IP address */
	 struct in_addr *adptr;
	 while ((adptr = (struct in_addr *)(*(host_info->h_addr_list)++)) !=
		NULL)
	 {
	     printf("  Internet address: %s\n", inet_ntoa(*adptr));
	 }
     } // if (host_info != NULL)
     if (sendto(sockfd, mesg, n, 0, pcli_addr, clilen) != n)
          err_dump("dg_echo: sendto error");
   }

   /*
     sigflag -= 1;    // decrease the number of connections
   }
   */
}

void sigio_func()
// signal handler
{
   sigflag += 1;   // increase the number of connections
   cout << " sig " << sigflag << '\n';
}

void process()
{
  int i;

  cout << " input a number \n";
  cin >> i;
}