CycloneDDS TRANSIENT_LOCAL helloworld

publisher.c

// NOTE: modified version of 
// https://github.com/eclipse-cyclonedds/cyclonedds/tree/c261053186c455abc63ca5ac7d56c0808a59c364/examples/helloworld

#include "dds/dds.h"
#include "HelloWorldData.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main(int argc, char **argv)
{
  dds_entity_t participant;
  dds_entity_t topic;
  dds_entity_t writer;
  dds_return_t rc;
  dds_qos_t *qos;
  HelloWorldData_Msg msg;
  (void)argc;
  (void)argv;

  /* Create a Participant. */
  participant = dds_create_participant(1, NULL, NULL);
  if (participant < 0)
    DDS_FATAL("dds_create_participant: %s\n", dds_strretcode(-participant));

  /* Create a Topic. */
  topic = dds_create_topic(
      participant, &HelloWorldData_Msg_desc, "HelloWorldData_Msg", NULL, NULL);
  if (topic < 0)
    DDS_FATAL("dds_create_topic: %s\n", dds_strretcode(-topic));

  /* Create a Writer. */
  qos = dds_create_qos();
  dds_qset_reliability(qos, DDS_RELIABILITY_RELIABLE, DDS_SECS(10));
  dds_qset_durability(qos, DDS_DURABILITY_TRANSIENT_LOCAL);
  dds_qset_history(qos, DDS_HISTORY_KEEP_LAST, 10);
  dds_qset_durability_service(qos, DDS_SECS(60), DDS_HISTORY_KEEP_LAST, 10, 100, 100, 100);
  writer = dds_create_writer(participant, topic, qos, NULL);
  if (writer < 0)
    DDS_FATAL("dds_create_writer: %s\n", dds_strretcode(-writer));

  for (int i = 1; i < 100; i++)
  {
    char str[20];
    sprintf(str, "Hello World #%d", i);

    /* Create a message to write. */
    msg.userID = 1;
    msg.message = str;

    printf("=== [Publisher]  Writing : ");
    printf("Message (%" PRId32 ", %s)\n", msg.userID, msg.message);
    fflush(stdout);

    rc = dds_write(writer, &msg);
    if (rc != DDS_RETCODE_OK)
      DDS_FATAL("dds_write: %s\n", dds_strretcode(-rc));

    dds_sleepfor(DDS_SECS(1));
  }

  /* Deleting the participant will delete all its children recursively as well. */
  rc = dds_delete(participant);
  if (rc != DDS_RETCODE_OK)
    DDS_FATAL("dds_delete: %s\n", dds_strretcode(-rc));

  return EXIT_SUCCESS;
}

subscriber.c

// NOTE: modified version of 
// https://github.com/eclipse-cyclonedds/cyclonedds/tree/c261053186c455abc63ca5ac7d56c0808a59c364/examples/helloworld

#include "dds/dds.h"
#include "HelloWorldData.h"
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

/* An array of one message (aka sample in dds terms) will be used. */
#define MAX_SAMPLES 10

int main(int argc, char **argv)
{
  dds_entity_t participant;
  dds_entity_t topic;
  dds_entity_t reader;
  HelloWorldData_Msg *msg;
  void *samples[MAX_SAMPLES];
  dds_sample_info_t infos[MAX_SAMPLES];
  dds_return_t rc;
  dds_qos_t *qos;
  (void)argc;
  (void)argv;

  /* Create a Participant. */
  participant = dds_create_participant(2, NULL, NULL);
  if (participant < 0)
    DDS_FATAL("dds_create_participant: %s\n", dds_strretcode(-participant));

  /* Create a Topic. */
  topic = dds_create_topic(
      participant, &HelloWorldData_Msg_desc, "HelloWorldData_Msg", NULL, NULL);
  if (topic < 0)
    DDS_FATAL("dds_create_topic: %s\n", dds_strretcode(-topic));

  /* Create a reliable Reader. */
  qos = dds_create_qos();
  dds_qset_reliability(qos, DDS_RELIABILITY_RELIABLE, DDS_SECS(10));
  dds_qset_durability(qos, DDS_DURABILITY_TRANSIENT_LOCAL);
  dds_qset_history(qos, DDS_HISTORY_KEEP_LAST, 10);
  reader = dds_create_reader(participant, topic, qos, NULL);
  if (reader < 0)
    DDS_FATAL("dds_create_reader: %s\n", dds_strretcode(-reader));
  dds_delete_qos(qos);
  rc = dds_reader_wait_for_historical_data(reader, DDS_MSECS(1000));
  if (rc < 0)
    DDS_FATAL("dds_reader_wait_for_historical_data: %s\n", dds_strretcode(-rc));

  printf("\n=== [Subscriber] Waiting for a sample ...\n");
  fflush(stdout);

  /* Initialize sample buffer, by pointing the void pointer within
   * the buffer array to a valid sample memory location. */
  for (int i = 0; i < MAX_SAMPLES; i++)
  {
    samples[i] = HelloWorldData_Msg__alloc();
  }

  /* Poll until data has been read. */
  while (true)
  {
    /* Do the actual read.
     * The return value contains the number of read samples. */
    rc = dds_take(reader, samples, infos, MAX_SAMPLES, MAX_SAMPLES);
    if (rc < 0)
      DDS_FATAL("dds_read: %s\n", dds_strretcode(-rc));

    /* Check if we read some data and it is valid. */
    if ((rc > 0) && (infos[0].valid_data))
    {
      printf("= %d samples received\n", rc);
      /* Print Messages. */
      for (int i = 0; i < rc; i++)
      {
        msg = (HelloWorldData_Msg *)samples[i];
        printf("=== [Subscriber] Received : ");
        printf("Message (%" PRId32 ", %s)\n", msg->userID, msg->message);
        fflush(stdout);
      }
      // break;
    }
    else
    {
      /* Polling sleep. */
      dds_sleepfor(DDS_MSECS(20));
    }
  }

  /* Free the data location. */
  HelloWorldData_Msg_free(samples[0], DDS_FREE_ALL);

  /* Deleting the participant will delete all its children recursively as well. */
  rc = dds_delete(participant);
  if (rc != DDS_RETCODE_OK)
    DDS_FATAL("dds_delete: %s\n", dds_strretcode(-rc));

  return EXIT_SUCCESS;
}