getopt broken for nn_sub

[nickdesaulniers]

See the discussion here. This needs to be fixed: #46 (comment)

http://nanomsg.org/v0.2/nn_setsockopt.3.html
http://nanomsg.org/v0.2/nn_getsockopt.3.html

[reqshark]

right now we're subscribing to all msgs, i.e., the subscription key is an empty string.

should that choice be determined by the user?

[reqshark]

@nickdesaulniers, we need to implement any socket subscription tracking at the JavaScript level.

Nanomsg was not designed to keep track of that.

And it looks like this was a deliberate choice: nn_getsockopt() does not return subscription lists, or anything but an err for that matter, see when this was discussed nanomsg/nanomsg#203

[nickdesaulniers]

Also related is PR #37 . I'm getting a really bad feeling about this API. Apparently, you set a socket option on the subscriber, which allows it to ignore the first word in a message. I would have expected you to set the same topic on the publisher, but this is not the case. I'll need to spend more time figuring this out, but I really think this feature is broken upstream. At the bare minimum, the API makes it ambiguous for language binding maintainers to pass an int vs char[].

test_case.c:

// clang test_case.c -lnanomsg -o test_case && ./test_case
#include <pthread.h> // pthread_t, pthread_create, pthread_join
#include <stdio.h> // printf
#include <assert.h> // assert
#include <string.h> // strnlen, memset
#include <unistd.h> // usleep
#include "nanomsg/nn.h"
#include "nanomsg/pubsub.h"

// Shared memory
const char* addr = "tcp://127.0.0.1:7777";
//

void* publisher (void* data) {
  printf("hello from publisher thread\n");

  int sock = nn_socket(AF_SP, NN_PUB);
  assert(sock >= 0);

  assert(nn_bind(sock, addr) >= 0);

  const char* msg1 = "topic.A hello world";
  const char* msg2 = "topic.B goodbye world";

  while (1) {
    int bytes = nn_send(sock, msg1, strnlen(msg1, 200), 0);
    printf("sent: %s\n", msg1);
    bytes = nn_send(sock, msg2, strnlen(msg2, 200), 0);
    printf("sent: %s\n", msg2);
    /*usleep(10000); // 10ms*/
    sleep(1);
  }

  nn_shutdown(sock, 0);

  return NULL;
}

void* subscriber (void* data) {
  printf("hello from subscriber thread\n");

  int sock = nn_socket(AF_SP, NN_SUB);
  assert(sock >= 0);

  assert(nn_setsockopt(sock, NN_SUB, NN_SUB_SUBSCRIBE, "topic.A", 0) >= 0);
  assert(nn_connect(sock, addr) >= 0);

  char buf [200];
  while (1) {
    int bytes = nn_recv(sock, &buf, 200, 0);

    printf("received: %s\n", buf);
    /*nn_freemsg(&buf);*/
    memset(&buf, 0, 200);
  }

  nn_shutdown(sock, 0);

  return NULL;
}

int main () {
  pthread_t p, s;
  assert(pthread_create(&p, NULL, publisher, NULL) == 0);
  assert(pthread_create(&s, NULL, subscriber, NULL) == 0);
  assert(pthread_join(p, NULL) == 0);
  assert(pthread_join(s, NULL) == 0);
}

I would have expected the topic.B messages to be filtered out, but this is not the case.

[reqshark]

wait a minute, so with that code you're not able to receive msg2 are you?

[nickdesaulniers]

With that code, I do receive msg2, so either filtering does not work, or does not work as I'm expecting.

[nickdesaulniers]

dupe #31