Getting response in simple_udp_connection - c

Question

I have a code in contiki cooja. I have 2 sending nodes and 2 receiving nodes as you can see in the picture1. the broadcast senders and receivers are as follows.
#include "contiki.h"
#include "lib/random.h"
#include "sys/etimer.h"
#include "net/ip/uip.h"
#include "net/ipv6/uip-ds6.h"
#include "net/ip/uip-debug.h"
#include "simple-udp.h"
#include <stdio.h>
#include <string.h>
#define SEND_INTERVAL (20 * CLOCK_SECOND)
#define SEND_TIME (random_rand() % (SEND_INTERVAL))
static struct simple_udp_connection broadcast_connection;
/*---------------------------------------------------------------------------*/
PROCESS(broadcast_example_process, "UDP broadcast example process");
AUTOSTART_PROCESSES(&broadcast_example_process);
/*---------------------------------------------------------------------------*/
static void
receiver(struct simple_udp_connection *c,
const uip_ipaddr_t *sender_addr,
uint16_t sender_port,
const uip_ipaddr_t *receiver_addr,
uint16_t receiver_port,
const uint8_t *data,
uint16_t datalen)
{
printf("Data received from ");
uip_debug_ipaddr_print(sender_addr);
printf(" on port %d from port %d with length %d: %s \n",
receiver_port, sender_port, datalen, data);
}
/*---------------------------------------------------------------------------*/
PROCESS_THREAD(broadcast_example_process, ev, data)
{
static struct etimer periodic_timer;
static struct etimer send_timer;
uip_ipaddr_t addr;
char message[20];
sprintf(message," hello ");
PROCESS_BEGIN();
simple_udp_register(&broadcast_connection, 1234,
NULL, 1900,
receiver);
etimer_set(&periodic_timer, SEND_INTERVAL);
while(1) {
PROCESS_WAIT_EVENT_UNTIL(etimer_expired(&periodic_timer));
etimer_reset(&periodic_timer);
etimer_set(&send_timer, SEND_TIME);
PROCESS_WAIT_EVENT_UNTIL(etimer_expired(&send_timer));
printf("Sending broadcast\n");
uip_create_linklocal_allnodes_mcast(&addr);
simple_udp_sendto(&broadcast_connection, message , strlen(message) , &addr);
}
PROCESS_END();
}
/*---------------------------------------------------------------------------*/
and receivers:
#include "contiki.h"
#include "lib/random.h"
#include "sys/ctimer.h"
#include "sys/etimer.h"
#include "net/ip/uip.h"
#include "net/ipv6/uip-ds6.h"
#include "simple-udp.h"
#include "net/ip/uip-debug.h"
#include <stdio.h>
#include <string.h>
#define UDP_PORT 1900
static struct simple_udp_connection broadcast_connection;
/*---------------------------------------------------------------------------*/
PROCESS(broadcast_example_process, "UDP broadcast example process");
AUTOSTART_PROCESSES(&broadcast_example_process);
/*---------------------------------------------------------------------------*/
static void
receiver(struct simple_udp_connection *c,
const uip_ipaddr_t *sender_addr,
uint16_t sender_port,
const uip_ipaddr_t *receiver_addr,
uint16_t receiver_port,
const uint8_t *data,
uint16_t datalen)
{
printf("Data received from ");
uip_debug_ipaddr_print(sender_addr);
printf(" on port %d from port %d with length %d: %s \n",
receiver_port, sender_port, datalen, data);
/* this line should work,right?*/
simple_udp_sendto(&broadcast_connection, "hello",5, sender_addr);
}
/*---------------------------------------------------------------------------*/
PROCESS_THREAD(broadcast_example_process, ev, data)
{
PROCESS_BEGIN();
simple_udp_register(&broadcast_connection, 1900,
NULL, 1234,
receiver);
while(1) {
PROCESS_WAIT_EVENT();
}
PROCESS_END();
}
/*---------------------------------------------------------------------------*/
Now the problem is replying to the sender. I want each receiver node reply to the sender which has sent that message to it.
I don't know how to do that?
simple_udp_sendto() does not work.Can I use this function for this job? How should I use that?

Answer 1

You normally have an RDC function : packet_received. When an IT trigger, packet_received is called with the data in ptr. You just have to send again by reading the address of the sender.
Edit : you probably have a packet_received on the network layer, with same function. If you don't, you should implements one.