/***************************************************************************

   udplisten    Designed as a simple class example.  The program waits for
                a request and sends it back to sender.

   This program expects one argument:
   udplisten <hostname> 
   The argument says where the server is

   Version 1.0   October, 2002 Yvan Petillot
****************************************************************************/
#include       <sys/types.h>
#include       <fcntl.h>
#include       <netdb.h>
#include       <sys/socket.h>
#include       <netinet/in.h>
#include       <unistd.h>
#include       <string.h>
#include       <errno.h>
#include       <stdio.h>
#include       <stdlib.h>

#define         TRUE            1
#define         FALSE           0
#define         BUFFER_SIZE     100
#define         PORT1           10000
#define         PORT2           10000

void    SysError( char * );

/* Main Program */
main ( int argc, char *argv[] )
{
  int                count;
  long               input_value;
  int                family = AF_INET;       /* The default for most cases */
  int                type   = SOCK_DGRAM;    /* Says it's a UDP connection */
  int                result;
  struct sockaddr_in my_addr;                /* Structure storing socket info */
  struct sockaddr_in their_addr;                /* Structure storing socket info */
  int                lsa = sizeof(my_addr);
  int                fd;   /* Socket id. On Unix a socket is a file descriptor */
  char               console_buffer[BUFFER_SIZE];
  char               ip_input_buffer[BUFFER_SIZE];
  char               ip_output_buffer[BUFFER_SIZE];
  struct hostent     *host;
  int on;
  
  /* Checks first we have the correct number of arguments */
  if ( argc < 2 ) {
    printf( "The program expects arguments\n" );
    printf( "udp <machine_name>\n" );
    exit(0);
  }

  if ((host = gethostbyname(argv[1])) == (struct hostent *)NULL) 
    {
      SysError("Gethostbyname failed");
    }
  /* Create socket*/
  if ((fd = socket (family, type, 0)) < 0)
    {
      SysError ("Error on socket");
    }
  /* Fills my_addr socket structure with correct fields */
  my_addr.sin_family       = family;
  my_addr.sin_port         = PORT1;              
  my_addr.sin_addr.s_addr  = htonl(INADDR_ANY); /* the kernel assigns the IP addr*/
   /* Fills their socket structure with correct fields */
  their_addr.sin_family       = family;
  their_addr.sin_port         = PORT2;             
  memcpy((char *)&their_addr.sin_addr, (char *)host->h_addr, host->h_length);
  
  on = 1;
  setsockopt(fd,SOL_SOCKET,SO_REUSEADDR,&on,sizeof(on));
  setsockopt(fd,SOL_SOCKET,SO_BROADCAST,&on,sizeof(on));

  /* First bind fd and sa structure*/ 
  if (bind (fd, (struct sockaddr *)&my_addr, sizeof(my_addr) ) == -1)
    SysError ("Error on bind");
  
  
  /* While client is sending info  This is blocking*/ 
  while (TRUE )
    {
      bzero( ip_input_buffer, sizeof( ip_input_buffer ));
      count = recvfrom( fd, ip_input_buffer,sizeof(ip_input_buffer),0,&their_addr,sizeof(their_addr));
      if (count ==0) break;
      /* Make sure output buffer is empty */
      bzero( ip_output_buffer, sizeof( ip_output_buffer ));
      /* Put output value in output buffer */
      printf("Received:%s\n",ip_input_buffer);
      strcpy(ip_output_buffer,ip_input_buffer);
      /* Send value back to client */
      /*if ( sendto(fd, ip_output_buffer, strlen(ip_output_buffer), 0,&their_addr,sizeof(their_addr) ) <= 0 )
	SysError( "Error on send" );*/
      
    }                           /* End of while recv is successful */
  close (fd);
}                                               
/* End of main          */



void    SysError( char *string )
{
  printf( "Error found:  String given is --> %s\n", string );
  exit(0);
}