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/*  Code with elevated privileges  */

int establish() 
{
  struct sockaddr_in sa;              /*  This will store the listening socket's address  */
  int s;                              /*  This will hold the listening socket  */

  /* Fill up the structure with address and port number */

  sa.sin_port = htons(portnum);

  /* Other system calls like socket() */

  if (bind(s, (struct sockaddr *) &sa, sizeof(struct sockaddr_in)) < 0)  { 
    /* Perform cleanup */  
  }

  /* Return */  
}

int main(void)
 {
   int s = establish();

   if (setuid(getuid()) == -1) {   /* Drop privileges permanently */
   {
        /*  Handle the error  */
   }

  /* Block with accept() until a client connects */
      
   switch(fork())
   {
      case -1: /* Error, clean up and quit */
      case  0: /* Close all open file descriptors
                * This is the child, handle the client 
                */
      default: /* This is the parent, continue blocking */
   }
}