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

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;
}

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 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!

• Do not use blocking receive in sockets that are created in a separate thread
• DO set linger to 0 in sockets that send, but make sure not to close the socket until you are ready to exit or the socket has successfully sent all it's messages
• Close the socket in the thread that created it, not in the main thread
• Close the context after all the threads have been closed

Finally, see the various answers that address this issue of "infinite wait":
stackoverflow[dot]com/questions/7538988/zeromq-how-to-prevent-infinite-wait

My architecture is also spread over multiple pc's and VM's, so I'm sure that plays some role in it, but I'm not seeing the sub-millisecond response times I was expecting. Roundtrip message times seem to be in the 20-25ms range using the examples provided. Adding my own logic to these provided examples obviously adds more latency, but I'm wondering if these numbers that I'm seeing are expected or not.

Below are the figures

16 cpu machine
./remote_lat tcp://127.0.0.1:5555 30 1000

message size: 30 [B] roundtrip count: 1000 average latency: 97.219 [us]

single cpu machine
/remote_lat tcp://127.0.0.1:5555 30 1000

message size: 30 [B] roundtrip count: 1000 average latency: 27.195 [us]

how is number of cpu making difference here?This is repeating in ubuntu ,red hat,centos
using libzmq 4.2.5

we have a difficult to find problem with a Python script, where an CNN for license plate recognition runs using Intel OpenVino and the communication to other programs is done using ZeroMQ. We are not sure what causes the problem, but as it causes so much network traffic that other PCs cannot communicate anymore, a problem with ZeroMQ seems possible.

Problem description:

We have a Python script, which runs 3 different CNNs using the Inference Engine from OpenVino 2018R5 on images from Ethernet cameras, which are retrieved with OpenCV VideoCapture. In addition ZeroMQ is used to pass results to other programs (via tcp). The used hardware is either an Intel NUC7BNH, an NUC7DNH or an NUC8BEH (on the NUC8 no freeze was observed until now). The OS is an Ubuntu 16.04 (with patched kernel 4.7.0.intel.r5.0 or kernel 4.15.0-15-generic (freezes happen less frequent with kernel 4.15). The script is running multiple times in separated Docker containers together with programs in other docker containers.

What happens is that the Linux freezes randomly after some time (sometimes after a few minutes, sometimes after a few hours but also two are now running for many days without a problem). When it freezes no ACPI shutdown works, the screen freezes and even the Magic SysRq keys have no effect. A strange side effect is that a lot of network traffic is created (so much traffic that the network dies and no PC on the switch can communicate). The logs (kern.log, syslog) show nothing special.

If anyone observed a similar problem or has an idea, what can cause this behavior, please let me know.

Greetings,

Thomas

I am trying out 0mq for Python <-> C++ IPC. What is interesting, whenever I send a request shorter than 5 characters from Python client to C++ server I get interesting result:
H+t
instead of just
H

But if I have at least 5 characters the message is parsed correctly… For Hello and longer I get what I send.
I don't define the buffer length anywhere so I am wondering.

In C++ server code looks like:

 zmq::message_t request; // Wait for next request from client socket_.recv (&request); std::istringstream iss(static_cast<char*>(request.data())); std::string message; iss >> message; std::cout << "Received " << message << std::endl; // here I get strange output! // Do some 'work' sleep(1); // Send reply back to client ...

 print("Sending request to C++") self.socket.send_string("H") # Get the reply. message = self.socket.recv() print("Received reply [ {} ]".format(message.decode('utf-8')))

If I send short message from C++ to Python it is parsed correctly though… Interesting.
I am sending long messages so actually it shouldn't be that terrible atm, but it may become problematic at some point.

Thank you for any insight!

Yet, there are cases where you need these working threads to maintain a common control state that rarly changes.
How would you suggest to approach this issue?

Regards,
Tal.

00 KERNELBASE!RaiseException+0x68
01 zmq::zmq_abort(char * errmsg_ = <Value unavailable error>)+0x21 [objdir-windows-msvc-14.0.x86_64\build\libzmq\src\err.cpp @ 89]
02 zmq::tcp_read(unsigned int64 s_ = <Value unavailable error>, void * data_ = <Value unavailable error>, unsigned int64 size_ = <Value unavailable error>)+0xa9 [objdir-windows-msvc-14.0.x86_64\build\libzmq\src\tcp.cpp @ 276]
03 zmq::stream_engine_t::in_event(void)+0x132 [objdir-windows-msvc-14.0.x86_64\build\libzmq\src\stream_engine.cpp @ 318]
04 zmq::select_t::trigger_events(class std::vector<zmq::select_t::fd_entry_t,std::allocator<zmq::select_t::fd_entry_t> > * fd_entries_ = 0x0000019d`323400c8, struct zmq::select_t::fds_set_t * local_fds_set_ = 0x0000006f`e3f9fb90, int event_count_ = 0n2)+0x74 [objdir-windows-msvc-14.0.x86_64\build\libzmq\src\select.cpp @ 122]
05 zmq::select_t::select_family_entry(struct zmq::select_t::family_entry_t * family_entry_ = 0x0000019d`323400c8, int max_fd_ = 0n0, bool use_timeout_ = <Value unavailable error>, struct timeval * tv_ = 0x0000006f`e3fffc98)+0xe9 [objdir-windows-msvc-14.0.x86_64\build\libzmq\src\select.cpp @ 404]
06 zmq::select_t::loop(void)+0x352 [objdir-windows-msvc-14.0.x86_64\build\libzmq\src\select.cpp @ 360]
07 thread_routine(void * arg_ = <Value unavailable error>)+0xd [objdir-windows-msvc-14.0.x86_64\build\libzmq\src\thread.cpp @ 47]
08 invoke_thread_procedure+0xe (Inline Function @ 00007ff7`50b99cf9) [d:\th\minkernel\crts\ucrt\src\appcrt\startup\thread.cpp @ 91]

Can anyone please help how to catch this exception ?

PUB Sender :

string sendHost = "norm:2,127.0.0.1:5556"; <NormNodeId>,<addr:port>
string tag = "MyTag";
string sentMessage = "HelloWorld";
string fullMessage = tag + sentMessage;

zmq::context_t *context = new zmq::context_t( 20 );

zmq::socket_t publisher( *context, ZMQ_PUB );
zmq_connect( publisher, sendHost.c_str() );

zmq_send( publisher,
fullMessage.c_str(),
fullMessage.size(),
0
);

SUB receiver:

char message[256];
string receiveHost = "norm:1,127.0.0.1:5556"; <NormNodeId>,<addr:port>
string tag = "MyTag";

zmq::context_t *context = new zmq::context_t( 20 );

zmq::socket_t subscriber( *context, ZMQ_SUB );
zmq_bind( subscriber, receiveHost.c_str() );
zmq_setsockopt( subscriber, ZMQ_SUBSCRIBE, tag.c_str(), tag.size() );

zmq_recv( subscriber,
message,
256,
0
);

cout « bytesReceived « endl;
cout « message « endl;

When I run the above code on a multi-threaded environment I get the following error printed to my console:

Proto Error: ProtoSocket::Bind() bind() error: Address already in use
Proto Fatal: NormSession::Open() error: rx_socket.Bind() error
Address already in use (src/session_base.cpp:692)
Aborted (core dumped)

I added some debugging statements. First I ran the receiver which binded successfully. After that I ran the sender which failed after the connect statement. I don't why is the error that bind failed while it was supposed to be just a connect request, not a bind one. Any help?

Now, in this POCO based windows service, I want to start a ZeroMQ library based Message Queue proxy to implement an XSUB/XPUB message queue.
From this service I will be running a xsub-xpub proxy.

More can be learnt here zguide.zeromq.org page:all.

For this I wrote another class ZeroMQProxy, which starts the proxy in the service's main function.

class ZeroMQProxy { private: zmq::context_t context; zmq::socket_t xsub; zmq::socket_t xpub; public: ZeroMQProxy() : context(1), xsub(context, ZMQ_XSUB), // Publisher End Proxy Sockets xpub(context, ZMQ_XPUB) // Subscriber End Proxy Sockets { } ~ZeroMQProxy() { } void proxyopen() { xsub.bind("tcp://*:5559"); xpub.bind("tcp://*:5560"); zmq::proxy(xsub, xpub, nullptr); } void proxyclose() { } }; class demopocoservice : public ServerApplication { private: bool _helpRequested; public: demopocoservice() : _helpRequested(false) { } ~demopocoservice() { } protected: void initialize(Application& self) { loadConfiguration(); ServerApplication::initialize(self); } void uninitialize() { ServerApplication::uninitialize(); } void defineOptions(OptionSet& options) { ServerApplication::defineOptions(options); options.addOption( Option("help", "h", "poco display help") .required(false) .repeatable(false) .callback(OptionCallback<demopocoservice>( this, &demopocoservice::handleHelp))); } void handleHelp(const std::string& name, const std::string& value) { _helpRequested = true; displayHelp(); stopOptionsProcessing(); } void displayHelp() { HelpFormatter helpFormatter(options()); helpFormatter.setCommand(commandName()); helpFormatter.setUsage("OPTIONS"); helpFormatter.setHeader("poco: Zero message Queue."); helpFormatter.format(std::cout); } int main(const ArgVec& args) { if (!_helpRequested) { ZeroMQProxy zmqproxyObj; zmqproxyObj.proxyopen(); waitForTerminationRequest(); zmqproxyObj.proxyclose(); } return Application::EXIT_OK; } }; int main(int argc, char** argv) { cout << "Hello Poco ZMQ\n"; demopocoservice pobj; pobj.run(argc, argv); return 0; }

My aim was when I start the service then the zmq::proxy() should have started the proxy and when I stop the service then proxy should be closed along with the sockets.

Problem is zmq::proxy() does not return back. So I am not able to stop the service.
Even if I do net stop <service name> the waitForTerminationRequest() does not receive termination request because of zmq::proxy().

I had tried calling the proxy() in a poco runnable thread. But it did not help.

class ZMQThread : public Poco::Runnable { private: std::string name; int value; public: ZMQThread(const std::string& arg1, int arg2) : name(arg1), value(arg2) { } ~ZMQThread() { } void run() { ZeroMQProxy zmqproxyObj; zmqproxyObj.proxyopen(); } };

Then called the thread as

 MQThread mqOne("Poco One", 4); Poco::Thread threadOne; threadOne.start(mqOne); threadOne.join();

What should I do to stop/close the proxy when I stop the service?

Now, in this POCO based windows service, I want to start a ZeroMQ library based Message Queue proxy to implement an XSUB/XPUB message queue.
From this service I will be running a xsub-xpub proxy.

More can be learnt here zguide.zeromq.org page:all.

For this I wrote another class ZeroMQProxy, which starts the proxy in the service's main function.

class ZeroMQProxy { private: zmq::context_t context; zmq::socket_t xsub; zmq::socket_t xpub; public: ZeroMQProxy() : context(1), xsub(context, ZMQ_XSUB), // Publisher End Proxy Sockets xpub(context, ZMQ_XPUB) // Subscriber End Proxy Sockets { } ~ZeroMQProxy() { } void proxyopen() { xsub.bind("tcp://*:5559"); xpub.bind("tcp://*:5560"); zmq::proxy(xsub, xpub, nullptr); } void proxyclose() { } }; class demopocoservice : public ServerApplication { private: bool _helpRequested; public: demopocoservice() : _helpRequested(false) { } ~demopocoservice() { } protected: void initialize(Application& self) { loadConfiguration(); ServerApplication::initialize(self); } void uninitialize() { ServerApplication::uninitialize(); } void defineOptions(OptionSet& options) { ServerApplication::defineOptions(options); options.addOption( Option("help", "h", "poco display help") .required(false) .repeatable(false) .callback(OptionCallback<demopocoservice>( this, &demopocoservice::handleHelp))); } void handleHelp(const std::string& name, const std::string& value) { _helpRequested = true; displayHelp(); stopOptionsProcessing(); } void displayHelp() { HelpFormatter helpFormatter(options()); helpFormatter.setCommand(commandName()); helpFormatter.setUsage("OPTIONS"); helpFormatter.setHeader("poco: Zero message Queue."); helpFormatter.format(std::cout); } int main(const ArgVec& args) { if (!_helpRequested) { ZeroMQProxy zmqproxyObj; zmqproxyObj.proxyopen(); waitForTerminationRequest(); zmqproxyObj.proxyclose(); } return Application::EXIT_OK; } }; int main(int argc, char** argv) { cout << "Hello Poco ZMQ\n"; demopocoservice pobj; pobj.run(argc, argv); return 0; }

My aim was when I start the service then the zmq::proxy() should have started the proxy and when I stop the service then proxy should be closed along with the sockets.

Problem is zmq::proxy() does not return back. So I am not able to stop the service.
Even if I do net stop <service name> the waitForTerminationRequest() does not receive termination request because of zmq::proxy().

I had tried calling the proxy() in a poco runnable thread. But it did not help.

class ZMQThread : public Poco::Runnable { private: std::string name; int value; public: ZMQThread(const std::string& arg1, int arg2) : name(arg1), value(arg2) { } ~ZMQThread() { } void run() { ZeroMQProxy zmqproxyObj; zmqproxyObj.proxyopen(); } };

Then called the thread as

MQThread mqOne("Poco One", 4); Poco::Thread threadOne; threadOne.start(mqOne); threadOne.join();

What should I do to stop/close the proxy when I stop the service?

software.opensuse .org/download.html?project=home%3Abluca%3Azmqers&package=libtldk-dev

You can then link to the tldk libraries with pkgconfig —libs tldk

If we restart the Receiver, application now receives the packets, but it won't be a solution. I tried with various ZMQ_RATE in both Sender & Receiver side.

Issue:

Sender sends almost 300,000 packets with following socket options, but Receiver stuck in between & not receiving all the packets.

Environment Setup:

( Sender & Receiver connected within the single subnet using D-Link switch. Media speed is 1Gbps )

Code Snippet

Sender: JZMQ ( ZMQ C library, openPGM )
JZMQ Sender:
ZMQ.Context context = ZMQ.context(1);
ZMQ.Socket socket = context.socket(ZMQ.PUB);
socket.setRate(80000);
socket.setRecoveryInterval(60*60);
socket.setSendTimeOut(-1);
socket.setSendBufferSize(1024*64);
socket.bind("pgm:local_IP;239.255.0.20:30001");

byte[] bytesToSend = new byte[1024];
int count = 0;
while(count < 300000) {
socket.send(bytesToSend, 0);
count++;
}

//Receiver: ZMQ C++ ( ZMQ C library, openPGM )

// ZMQCPP-PGM-receive.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <stdio.h>
#include "zmq.hpp"

int main(int argc, char* argv[]) {
try {

zmq::context_t context(1);

// Socket to talk to server
printf ("Connecting to server…");

zmq::socket_t *s1 = new zmq::socket_t(context, ZMQ_SUB);

int recvTimeout = 3000;
s1->setsockopt(ZMQ_RCVTIMEO,&recvTimeout,sizeof(int));

int recvRate = 80000;
s1->setsockopt(ZMQ_RATE,&recvRate,sizeof(int));

int recvHwMark = 5000;
s1->setsockopt ( ZMQ_RCVHWM, &recvHwMark, sizeof(int) );

int recsec = 60 * 60;
// s1->setsockopt(ZMQ_RECOVERY_IVL,&recsec,sizeof(recsec));

s1->connect("pgm://local_IP;239.255.0.20:30001");

s1->setsockopt (ZMQ_SUBSCRIBE, NULL, 0);

printf ("done. \n");
int seq=0;
while(true) {

zmq::message_t msgbuff;

int ret = s1->recv(&msgbuff,0);
if(!ret)
{
printf ("Received not received timeout\n");
continue;
}

printf ("Seq(%d) Received data size=%d\n",seq,msgbuff.size());
++seq;
}
//Socket close to be handled
}
catch( zmq::error_t &e ) {
printf ("An error occurred: %s\n", e.what());
return 1;
}
catch( std::exception &e ) {
printf ("An error occurred: %s\n", e.what());
return 1;
}
return 0;
}

What can be the issue?

For example: DEALER (client) - ROUTER - DEALER (service), i need to connect clients with internal security policy… for example i need one client with identity "test", and dont accept other identity's. How to?