Thank you, Pieter. So, this is what I've ended up with:
int read_zmq_connections() {
zmq_pollitem_t items [] = {
{ zmq_responder, 0, ZMQ_POLLIN, 0 }
};
errno = 0;
int ret = 0;
while ( errno == 0 ) {
zmq_msg_t message;
int rc = zmq_poll(items, 1, 0);
if (rc == -1) break;
if (items[0].revents & ZMQ_POLLIN) {
zmq_msg_init(&message);
int size = zmq_msg_recv(&message, zmq_responder, 0);
if (size == -1)
break;
char *str = malloc(size + 1);
memcpy(str, zmq_msg_data(&message), size);
str[size] = 0;
add_remote_account(str);
free(str);
zmq_msg_close(&message);
++ret;
} else {
break;
}
}
return ret;
}
I replaced the helper functions with the core API methods, as I didn't want to
be limited to 255 character strings. The packets I'm sending aren't bit, but
may be a little bigger (100 - 350 chars approx).
I'll give this a thorough testing in the morning, but I'm currently happier
with it right now.
Thanks again,
Lee
On 19 Feb 2013, at 22:11, Pieter Hintjens <[email protected]> wrote:
> Lee,
>
> For what it's worth, this is the poll construct I always use:
>
> while (true) {
> zmq_pollitem_t items [] = {
> { onesocket, 0, ZMQ_POLLIN, 0 }
> { twosocket, 0, ZMQ_POLLIN, 0 }
> };
> // Calculate timeout here or use 0 for infinity
> int rc = zmq_poll (items, 1, mytimeout);
> if (rc == -1)
> break; // Always check for Ctrl-C
>
> if (items [0].revents & ZMQ_POLLIN) {
> zmsg_t *msg = zmsg_recv (onesocket);
> if (!msg)
> break; // Always check for Ctrl-C
> // Process message
> zmsg_destroy (&msg);
> }
> // Test all sockets (not an else here)
> if (items [1].revents & ZMQ_POLLIN) {
> ...
> }
> // Do regular maintenance if needed
> }
>
> -Pieter
>
> On Tue, Feb 19, 2013 at 11:04 PM, Lee Sylvester <[email protected]>
> wrote:
>> Okay, so this brings me kinda to where I was before:
>>
>> int read_zmq_connections() {
>> zmq_pollitem_t items [] = {
>> { zmq_responder, 0, ZMQ_POLLIN, 0 }
>> };
>> errno = 0;
>> int ret = 0;
>> while ( errno == 0 ) {
>> zmq_poll(items, 1, 0);
>> if (items [0].revents & ZMQ_POLLIN) {
>> char *str = s_recv(zmq_responder);
>> add_remote_account(str);
>> free(str);
>> ++ret;
>> } else {
>> break;
>> }
>> }
>> return ret;
>> }
>>
>> So, I poll the events and, if an error occurs or if there is no event, then
>> I return the number of messages retrieved. Have I missed something?
>>
>> Thanks,
>> Lee
>>
>>
>> On 19 Feb 2013, at 17:11, Charles Remes <[email protected]> wrote:
>>
>>> It looks better except for the use of "size" in the loop control. The
>>> return code from zmq_poll is the *number of sockets* that have pending
>>> events. The way you are using it appears as though you believe the return
>>> code indicates the *number of messages* which is incorrect. The way the
>>> loop is written now, it will loop once and exit at most.
>>>
>>>
>>> On Feb 19, 2013, at 10:29 AM, Lee Sylvester <[email protected]> wrote:
>>>
>>>> Okay, thank you. So I now have the following:
>>>>
>>>> int read_zmq_connections() {
>>>> zmq_pollitem_t items [] = {
>>>> { zmq_responder, 0, ZMQ_POLLIN, 0 }
>>>> };
>>>> errno = 0;
>>>> int ret = 0, size = zmq_poll(items, 1, 0);
>>>> zmq_msg_t message;
>>>> while ( size > 0 && errno == 0 ) {
>>>> char *str = s_recv(zmq_responder);
>>>> parse_new_data(str);
>>>> free(str);
>>>> ++ret;
>>>> --size;
>>>> }
>>>> return ret;
>>>> }
>>>>
>>>> I'm going to test it a little later once I've written my client code. :-)
>>>>
>>>> Thanks again.
>>>>
>>>> Cheers,
>>>> Lee
>>>>
>>>>
>>>>
>>>> On 19 Feb 2013, at 16:21, Charles Remes <[email protected]> wrote:
>>>>
>>>>> Yes, you are missing out on being able to differentiate between reads &
>>>>> writes since you aren't checking the revents. However, in your case you
>>>>> only have a single socket and you only register for POLLIN, so you can
>>>>> just use the return code and skip the hard stuff. Any time it returns 1
>>>>> then you know that your socket is readable.
>>>>>
>>>>>
>>>>> On Feb 19, 2013, at 10:18 AM, Lee Sylvester <[email protected]>
>>>>> wrote:
>>>>>
>>>>>> Okay, thanks. I'm looking at the reference and I can see that zmq_poll
>>>>>> returns the number of items, but it feels like I'm missing something
>>>>>> when I rely on that :-S
>>>>>>
>>>>>> Lee
>>>>>>
>>>>>>
>>>>>> On 19 Feb 2013, at 15:52, Charles Remes <[email protected]> wrote:
>>>>>>
>>>>>>> Hmmm, I'm not sure that's exactly right.
>>>>>>>
>>>>>>> The basic idea is that you want to check the return code from zmq_poll.
>>>>>>> If it is greater than 0, then the socket can be read from. You should
>>>>>>> then read from the socket until no more messages are available. I don't
>>>>>>> know how it works with the #s_recv() function (presumably that is part
>>>>>>> of the czmq binding) but you want to read until the socket is empty or
>>>>>>> you get EAGAIN. Perhaps that function does that for you under the
>>>>>>> covers.
>>>>>>>
>>>>>>> So, the loop should be around reading from the socket and *not* around
>>>>>>> zmq_poll. Does that make sense?
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On Feb 19, 2013, at 9:16 AM, Lee Sylvester <[email protected]>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> Thank you, that's great. So, based on what I've read, does this look
>>>>>>>> correct for what I'm trying to accomplish?
>>>>>>>>
>>>>>>>> int read_zmq_connections() {
>>>>>>>> zmq_pollitem_t items [] = {
>>>>>>>> { zmq_responder, 0, ZMQ_POLLIN, 0 }
>>>>>>>> };
>>>>>>>> while (1) {
>>>>>>>> zmq_msg_t message;
>>>>>>>> zmq_poll(items, 1, 0);
>>>>>>>> if (items[0].revents & ZMQ_POLLIN) {
>>>>>>>> char *str = s_recv(zmq_responder);
>>>>>>>> parse_new_data(str);
>>>>>>>> free(str);
>>>>>>>> } else {
>>>>>>>> break;
>>>>>>>> }
>>>>>>>> }
>>>>>>>> return 0;
>>>>>>>> }
>>>>>>>>
>>>>>>>> Thanks,
>>>>>>>> Lee
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> On 19 Feb 2013, at 14:52, Charles Remes <[email protected]> wrote:
>>>>>>>>
>>>>>>>>> Take a look at the man page for zmq_poll. You can do a non-blocking
>>>>>>>>> poll for incoming messages on your socket. If it returns immediately
>>>>>>>>> with 0, then no sockets in your pollset have pending messages to read.
>>>>>>>>>
>>>>>>>>> Be aware that when zmq_poll does indicate that you have messages, you
>>>>>>>>> must read *all* of them from the socket before zmq_poll will work
>>>>>>>>> again. I'm pretty sure the man page explains this.
>>>>>>>>>
>>>>>>>>> Good luck.
>>>>>>>>>
>>>>>>>>> On Feb 19, 2013, at 8:44 AM, Lee Sylvester <[email protected]>
>>>>>>>>> wrote:
>>>>>>>>>
>>>>>>>>>> Hey guys,
>>>>>>>>>>
>>>>>>>>>> So, I've integrated ØMQ into my server. Now, I want to use ØMQ as a
>>>>>>>>>> means to supply information to a HTTP server from a separate
>>>>>>>>>> management app. So, in theory, it will look something like this
>>>>>>>>>>
>>>>>>>>>> int read_zmq_connections() {
>>>>>>>>>> int ret = 0;
>>>>>>>>>> while (zmq_has_messages(zmq_responder)) {
>>>>>>>>>> char *str = s_recv(zmq_responder);
>>>>>>>>>> parse_new_data(str);
>>>>>>>>>> free(str);
>>>>>>>>>> ++ret;
>>>>>>>>>> }
>>>>>>>>>> return ret;
>>>>>>>>>> }
>>>>>>>>>>
>>>>>>>>>> This way, if there are no messages on zmq_responder, then the
>>>>>>>>>> function will simply return. What I don't know how to do (and can't
>>>>>>>>>> quite find) is how to check if messages exist on the connection.
>>>>>>>>>> Can anyone please point me in the right direction?
>>>>>>>>>>
>>>>>>>>>> The reason why I need this non-blocking is that I will only be
>>>>>>>>>> calling 'read_zmq_connections' approximately once every five minutes
>>>>>>>>>> and I don't want my app to hang while waiting for messages.
>>>>>>>>>>
>>>>>>>>>> Thanks loads in advance,
>>>>>>>>>> Lee
>>>>>>>>>> _______________________________________________
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>>>>>>>>>
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