zeromq

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time flies, this has become my yearly check

You're busy for thirteen years!

Almost 12… drum rolls

Hi there,
I am new why zmq and this is my first time with independent processors.
I'm not sure I can do what I want with ZMQ, that's why I would like your opinion.

Here is my case:
- First process (1): it runs continuously, it contains traffic that changes over time.
- Second process (2): it is a solver that ensures that there is no conflict in my traffic.

Currently, I use files to communicate my two processes. (1) refreshes every 10 seconds a traffic file and (2) reads it if it exists when it starts a new algorithm generation (I skip the details).
(2) very regularly updates a solution file, which (1) will read every 10 seconds.
These reads/writes are asynchronous and my current version is probably not 100% stable because you have to constantly check that there is no write when one reads and vice versa… You see.

I wanted to know if a double PUSH - PULL operations could work here, in your opinion?
A small detail bothers me: my solution file can change before (1) reads it (because a better solution is found) and therefore I would have to be able to delete elements in the queue if they have not yet been read …

Thank you in advance for your comments/advice/opinions.

Sier

11 :)

hello all
I am new to zeromq, tried to compile/run the server/client example in C.
While i was able to compile I had issues executing the server, got a seg fault on the assert(rc ==0) (see code below), wanted to ask what the purpose of the assertion was ?
I was able to get the example to work when I comment out the assert command

On Ubuntu 20.04 LTS, using czmq

// Hello World server
#include <czmq.h>

int main (void)
{
// Socket to talk to clients
zsock_t *responder = zsock_new (ZMQ_REP);
int rc = zsock_bind (responder, "tcp://*:5555");
assert (rc == 0);

while (1) {
char *str = zstr_recv (responder);
printf ("Received Hello\n");
sleep (1); // Do some 'work'
zstr_send (responder, "World");
zstr_free (&str);
}
return 0;
}

10!

Yep, almost 9 years.

This is an amazing article, very well written covering lot of aspects. Many thanks for sharing.

Nine years!

For those interested, I figured out my issue. I forgot to add the identity and empty frames at the beginning of the reply message.

The identity frame is necessary for the DealerSocket to figure out which caller's ReceiveReady event to invoke, so without those frames it will not invoke ANY RecieveReady events, as if the message wasn't even received. I am a little surprised that this socket didn't raise an exception indicating that the socket received a reply message that did not match up with a previously sent message (via the identity value).

I'm pretty sure I had the identity frame and empty frame at the beginning of the reply message, but I was switching back and forth between the Request/Response and Dealer/Router patterns and along the way I removed them thinking I was simplifying the reply message and forgot that they were necessary.

I am trying to use zmq with C# and Python and have run into an issue that I hoping someone can help me with. My DealerSocket's ReceiveReady event is not being invoked!

I am trying to implement an asynchronous client where a C#/NetMQ client sends a message to the Python/pyzmq 'server' and later gets a reply via a callback method.

On the C# side, I have a DealerSocket and I subscribe the method MyReceiveReady to the socket's ReceiveReady event. I also create a poller and add the client to the poller and I am calling the poller.RunAsync() method to start the poller. The client assembles a NetMQMessage and sends the message via the client.SendMultipartMessage(msg) method.

On the Python side, I have a RouterSocket that receives a message with the server.recv_multipart() method, performs some work with the contents of the message, then assembles a return message and replies to the client with the server.send_multipart(msg) method.

When I run the Python code and then the C# code, the C# client sends the message, the Python server receives the message and sends the reply, but the client's ReceiveReady event never invokes, so the client never receives the reply! If I implement the server in C# the client's event IS invoked, but, I have a requirement that the server be in Python and the client in C#.

Am I doing something wrong? Or, is this some deficiency or bug between NetMQ and pyzmq? Please help!