blocks|key|2822530|text|解决方案是轮询您的io_service，而不是run()。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2822531|有关poll()的一些信息，请查看this+solution。|offset|length|2822532|使用轮询而不是运行将允许您轮询zmq的连接，而不会出现任何阻塞问题。|2822533|entityMap|0|LINK|mutability|MUTABLE|url|http://www.boost.org/doc/libs/1_51_0/doc/html/boost_asio/reference/io_service/run/overload1.html|1|https://stackoverflow.com/questions/4705411/boostasio-io-service-run-vs-poll-or-how-do-i-integrate-boostasio-in-ma^0|0|2|6|0|H|D|1|0|0^^$0|@$1|2|3|4|5|6|7|R|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|S|8|@]|9|@$D|T|E|U|1|V]|$D|W|E|X|1|Y]]|A|$]]|$1|F|3|G|5|6|7|Z|8|@]|9|@]|A|$]]|$1|H|3|-4|5|6|7|10|8|@]|9|@]|A|$]]]|I|$J|$5|K|L|M|A|$N|O]]|P|$5|K|L|M|A|$N|Q]]]]

The solution is to poll your io_service as well instead of run().

Check out <a href="https://stackoverflow.com/questions/4705411/boostasio-io-service-run-vs-poll-or-how-do-i-integrate-boostasio-in-ma">this solution</a> for some <a href="http://www.boost.org/doc/libs/1_51_0/doc/html/boost_asio/reference/io_service/run/overload1.html" rel="nofollow noreferrer">poll()</a> info.

Using poll instead of run will allow you to poll zmq's connections without any blocking issues.

blocks|key|4946380|text|在阅读了文档here和here之后，特别是这一段|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|4946381|4946382|+ZMQ_FD:检索与套接字关联的文件描述符ZMQ_FD选项将检索与指定套接字关联的文件描述符。返回的文件描述符可用于将套接字集成到现有的事件循环中；通过使文件描述符准备好读取，ÖMQ库应以边缘触发的方式通知套接字上的任何未决事件。|blockquote|4946383|4946384|4946385|我认为您可以对每个zmq_pollitem_t使用null_buffers，并将事件循环推迟到io_service，完全绕过zmq_poll()。但是，上面提到的文档中似乎有一些警告，值得注意的是|style|CODE|4946386|4946387|能够从返回的文件描述符中读取并不一定表示可以从底层套接字读取消息，也不一定可以将消息写入底层套接字；应用程序必须通过后续的ZMQ_EVENTS选项检索实际的事件状态。|4946388|4946389|4946390|因此，当您的某个zmq套接字的处理程序被触发时，我认为在处理事件之前，您必须做更多的工作。未编译的伪代码如下|4946391|const+int+fd+=+getZmqDescriptorSomehow();
boost::asio::posix::stream_descriptor+socket(+_io_service,+fd+);
socket->async_read_some(
++++boost::asio::null_buffers(),
++++[=](const+boost::system::error_code&+error)
++++{
+++++++if+(!error)+{
+++++++++++//+handle+data+ready+to+be+read
+++++++}
+++++}
);|code-block|syntax|javascript|4946392|注意在这里你不需要使用lambda，成员函数的boost::bind就足够了。|4946393|entityMap|0|LINK|mutability|MUTABLE|url|http://api.zeromq.org/2-1:zmq-getsockopt|1|http://www.zeromq.org/area:faq|2|https://stackoverflow.com/a/4686523/283302^0|6|4|0|B|4|1|0|0|0|0|0|9|E|P|C|1B|A|1Q|A|P|C|2|0|0|0|0|0|0|0|N|B|0^^$0|@$1|2|3|4|5|6|7|1D|8|@]|9|@$A|1E|B|1F|1|1G]|$A|1H|B|1I|1|1J]]|C|$]]|$1|D|3|-4|5|6|7|1K|8|@]|9|@]|C|$]]|$1|E|3|F|5|G|7|1L|8|@]|9|@]|C|$]]|$1|H|3|-4|5|6|7|1M|8|@]|9|@]|C|$]]|$1|I|3|-4|5|6|7|1N|8|@]|9|@]|C|$]]|$1|J|3|K|5|6|7|1O|8|@$A|1P|B|1Q|L|M]|$A|1R|B|1S|L|M]|$A|1T|B|1U|L|M]|$A|1V|B|1W|L|M]]|9|@$A|1X|B|1Y|1|1Z]]|C|$]]|$1|N|3|-4|5|6|7|20|8|@]|9|@]|C|$]]|$1|O|3|P|5|G|7|21|8|@]|9|@]|C|$]]|$1|Q|3|-4|5|6|7|22|8|@]|9|@]|C|$]]|$1|R|3|-4|5|6|7|23|8|@]|9|@]|C|$]]|$1|S|3|T|5|6|7|24|8|@]|9|@]|C|$]]|$1|U|3|V|5|W|7|25|8|@]|9|@]|C|$X|Y]]|$1|Z|3|10|5|6|7|26|8|@$A|27|B|28|L|M]]|9|@]|C|$]]|$1|11|3|-4|5|6|7|29|8|@]|9|@]|C|$]]]|12|$13|$5|14|15|16|C|$17|18]]|19|$5|14|15|16|C|$17|1A]]|1B|$5|14|15|16|C|$17|1C]]]]

After reading the documentation <a href="http://api.zeromq.org/2-1:zmq-getsockopt" rel="nofollow noreferrer">here</a> and <a href="http://www.zeromq.org/area:faq" rel="nofollow noreferrer">here</a>, specifically this paragraph

<blockquote>
 ZMQ_FD: Retrieve file descriptor associated with the socket The ZMQ_FD
 option shall retrieve the file descriptor associated with the
 specified socket. The returned file descriptor can be used to
 integrate the socket into an existing event loop; the ØMQ library
 shall signal any pending events on the socket in an edge-triggered
 fashion by making the file descriptor become ready for reading.
</blockquote>

I think you can use <a href="https://stackoverflow.com/a/4686523/283302"><code>null_buffers</code></a> for every <code>zmq_pollitem_t</code> and defer the event loop to an <code>io_service</code>, completely bypassing <code>zmq_poll()</code> altogether. There appear to be some caveats in the aforementioned documentation however, notably

<blockquote>
 The ability to read from the returned file descriptor does not
 necessarily indicate that messages are available to be read from, or
 can be written to, the underlying socket; applications must retrieve
 the actual event state with a subsequent retrieval of the ZMQ_EVENTS
 option.
</blockquote>

So when the handler for one of your zmq sockets is fired, you'll have to do a little more work before handling the event I think. Uncompiled pseudo-code is below

<pre><code>const int fd = getZmqDescriptorSomehow();
boost::asio::posix::stream_descriptor socket( _io_service, fd );
socket-&gt;async_read_some(
 boost::asio::null_buffers(),
 [=](const boost::system::error_code&amp; error)
 {
 if (!error) {
 // handle data ready to be read
 }
 }
);
</code></pre>

note you don't have to use a lambda here, <code>boost::bind</code> to a member function would be sufficient.

blocks|key|4946435|text|最后，我想出了两种可能的解决方案：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4946436|在|4946437|Sam+Miller的文章中，我们通过acceptor和socket的.native()方法获取ASIO文件描述符，并将它们插入到zmq_pollitem_t|unordered-list-item|offset|length|style|CODE|4946438|数组中，从而使用ASIO|4946439|的事件循环。|4946440|4946441|我已经接受了Sam+Miller的回答，因为这对我来说是SCGI中不断创建和结束新连接的最佳解决方案。因此，处理每次更改的zmq_pollitem_t数组都是一件很麻烦的事情，可以通过使用ASIO事件循环来避免。|4946442|entityMap^0|0|0|J|8|S|6|Z|9|1T|E|0|0|0|0|1P|E|0^^$0|@$1|2|3|4|5|6|7|T|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|U|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|V|8|@$G|W|H|X|I|J]|$G|Y|H|Z|I|J]|$G|10|H|11|I|J]|$G|12|H|13|I|J]]|9|@]|A|$]]|$1|K|3|L|5|6|7|14|8|@]|9|@]|A|$]]|$1|M|3|N|5|F|7|15|8|@]|9|@]|A|$]]|$1|O|3|-4|5|6|7|16|8|@]|9|@]|A|$]]|$1|P|3|Q|5|6|7|17|8|@$G|18|H|19|I|J]]|9|@]|A|$]]|$1|R|3|-4|5|6|7|1A|8|@]|9|@]|A|$]]]|S|$]]

In the end I figured out there are two possible solutions:

<ul>
<li>Sam Miller's where we use the event loop of ASIO</li>
<li>The ZeroMQ's event loop by getting the ASIO file descriptors though the <code>.native()</code> methods of the <code>acceptor</code> and the <code>socket</code> and inserting them into the array of <code>zmq_pollitem_t</code></li>
</ul>

I have accepted the answer of Sam Miller as that's for me the best solution in SCGI case where constantly new connections are created and ended. Handling the thus every changing <code>zmq_pollitem_t</code> array is big hassle that can be avoided by using the ASIO event loop.

blocks|key|2822722|text|获取ZeroMQ的套接字是这场战斗中最小的一部分。ZeroMQ基于TCP之上的protocol，因此如果您选择此路线，您将不得不在自定义的Boost.Asio+io_service中重新实现ZeroMQ。在使用Boost.Asio创建异步ENet服务时，我遇到了同样的问题，首先只是尝试使用Boost.Asio+UDP服务捕获来自ENet客户端的流量。ENet是一种基于UDP的类似TCP的协议，所以我当时所做的就是捕获处于几乎无用状态的数据包。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|2822723|Boost.Asio是基于模板的，内置的io_+service使用模板基本上包装了系统套接字库来创建TCP和UDP服务。我的最后一个解决方案是创建一个自定义的io_service，它包装了ENet库而不是系统套接字库，允许它使用ENet的传输函数，而不必使用内置的UDP传输重新实现它们。|2822724|对于ZeroMQ也可以这样做，但ZeroMQ本身已经是一个非常高性能的网络库，它已经提供了异步I/O。我认为你可以通过使用ZeroMQ现有的API接收消息并将消息传递到io_service线程池中来创建一个可行的解决方案。这样，消息/任务仍将使用Boost.ASIO的反应器模式进行异步处理，而无需重写任何内容。ZeroMQ将提供异步I/O，Boost.Asio将提供异步任务处理程序/工作器。|2822725|现有的io_service仍然可以耦合到现有的TCP套接字，从而允许线程池处理TCP+(在本例中为HTTP)和ZeroMQ。在这样的设置中，完全可以让ZeroMQ任务处理程序访问TCP服务会话对象，从而允许您将ZeroMQ消息/任务的结果发送回TCP客户机。|2822726|下面只是为了说明这个概念。|2822727|//+Create+a+pool+of+threads+to+run+all+of+the+io_services.
std::vector<boost::shared_ptr<boost::thread>+>+threads;
for(std::size_t+i+=+0;+i+<+thread_pool_size_;+%2B%2Bi)+{
++++boost::shared_ptr<boost::thread>+thread(new+boost::thread(boost::bind(&boost::asio::io_service::run,+&io_service_)));
++++threads.push_back(thread);
}

while+(1)+{
++++char+buffer+[10];
++++zmq_recv+(responder_,+buffer,+10,+0);
++++io_service_.post(boost::bind(&server::handle_zeromq_message,+buffer,+this));
}|code-block|syntax|javascript|2822728|entityMap|0|LINK|mutability|MUTABLE|url|http://rfc.zeromq.org/spec:15|1|http://enet.bespin.org/Features.html^0|13|8|0|3B|4|1|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@$A|11|B|12|1|13]|$A|14|B|15|1|16]]|C|$]]|$1|D|3|E|5|6|7|17|8|@]|9|@]|C|$]]|$1|F|3|G|5|6|7|18|8|@]|9|@]|C|$]]|$1|H|3|I|5|6|7|19|8|@]|9|@]|C|$]]|$1|J|3|K|5|6|7|1A|8|@]|9|@]|C|$]]|$1|L|3|M|5|N|7|1B|8|@]|9|@]|C|$O|P]]|$1|Q|3|-4|5|6|7|1C|8|@]|9|@]|C|$]]]|R|$S|$5|T|U|V|C|$W|X]]|Y|$5|T|U|V|C|$W|Z]]]]

Obtaining the socket to ZeroMQ is the smallest part of the battle. ZeroMQ is based on a <a href="http://rfc.zeromq.org/spec:15" rel="nofollow">protocol</a> which is layered over TCP, so you will have to reimplement ZeroMQ within a custom Boost.Asio io_service if you go this route. I ran into the same problem when creating an asynchronous <a href="http://enet.bespin.org/Features.html" rel="nofollow">ENet</a> service using Boost.Asio by first simply trying to catch traffic from an ENet client using a Boost.Asio UDP service. ENet is a TCP like protocol layered over UDP, so all I achieved at that point was catching packets in a virtually useless state.

Boost.Asio is template based, and the built-in io_service's use templates to basically wrap the system socket library to create TCP and UDP service. My final solution was to create a custom io_service that wrapped the ENet library rather than the systems socket library, allowing it to use ENet's transport functions rather than having to reimplement them using the built-in UDP transport.

The same can be done for ZeroMQ, but ZeroMQ is already a very high performance network library in it's own right that already provides async I/O. I think you can create a viable solution by receiving messages using ZeroMQ's existing API and passing the messages into a io_service thread pool. That way messages/tasks will still be handled asynchronously using Boost.Asio's reactor pattern without having to re-write anything. ZeroMQ will provide the async I/O, Boost.Asio will provide the async task handlers/workers.

The existing io_service can still be coupled to an existing TCP socket as well, allowing the threadpool to handle both TCP (HTTP in your case) and ZeroMQ. It's entirely possible in such a setup for the ZeroMQ task handlers to access the TCP services session objects, allowing you to send results of the ZeroMQ message/task back to a TCP client.

The following is just to illustrate the concept.

<pre><code>// Create a pool of threads to run all of the io_services.
std::vector&lt;boost::shared_ptr&lt;boost::thread&gt; &gt; threads;
for(std::size_t i = 0; i &lt; thread_pool_size_; ++i) {
 boost::shared_ptr&lt;boost::thread&gt; thread(new boost::thread(boost::bind(&amp;boost::asio::io_service::run, &amp;io_service_)));
 threads.push_back(thread);
}

while (1) {
 char buffer [10];
 zmq_recv (responder_, buffer, 10, 0);
 io_service_.post(boost::bind(&amp;server::handle_zeromq_message, buffer, this));
}
</code></pre>

blocks|key|5035700|text|这个问题提出2年后，有人发布了一个项目，就是这样做的。这个项目在这里：https://github.com/zeromq/azmq。讨论该设计的博客帖子在这里：https://rodgert.github.io/2014/12/24/boost-asio-and-zeromq-pt1/。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|5035701|下面是从自述文件中复制的示例代码：|5035702|#include+<azmq/socket.hpp>
#include+<boost/asio.hpp>
#include+<array>

namespace+asio+=+boost::asio;

int+main(int+argc,+char**+argv)+{
++++asio::io_service+ios;
++++azmq::sub_socket+subscriber(ios);
++++subscriber.connect("tcp://192.168.55.112:5556");
++++subscriber.connect("tcp://192.168.55.201:7721");
++++subscriber.set_option(azmq::socket::subscribe("NASDAQ"));

++++azmq::pub_socket+publisher(ios);
++++publisher.bind("ipc://nasdaq-feed");

++++std::array<char,+256>+buf;
++++for+(;;)+{
++++++++auto+size+=+subscriber.receive(asio::buffer(buf));
++++++++publisher.send(asio::buffer(buf));
++++}
++++return+0;
}|code-block|syntax|javascript|5035703|看起来不错。如果您尝试，请在评论中让我知道它在2019年I+will+probably+try+in+a+couple+of+months+and+then+update+this+answer中是否仍然有效|5035704|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/zeromq/azmq|1|https://rodgert.github.io/2014/12/24/boost-asio-and-zeromq-pt1/|2|the+repo+is+stale,+last+commit+was+a+year+ago^0|Z|U|0|28|1R|1|0|0|0|S|1X|2|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@$A|Z|B|10|1|11]|$A|12|B|13|1|14]]|C|$]]|$1|D|3|E|5|6|7|15|8|@]|9|@]|C|$]]|$1|F|3|G|5|H|7|16|8|@]|9|@]|C|$I|J]]|$1|K|3|L|5|6|7|17|8|@]|9|@$A|18|B|19|1|1A]]|C|$]]|$1|M|3|-4|5|6|7|1B|8|@]|9|@]|C|$]]]|N|$O|$5|P|Q|R|C|$S|T]]|U|$5|P|Q|R|C|$S|V]]|W|$5|P|Q|R|C|$S|X]]]]

2 years after this question someone posted a project which does exactly this. The project is here: <a href="https://github.com/zeromq/azmq" rel="nofollow noreferrer">https://github.com/zeromq/azmq</a>. The blog post discussing the design is here: <a href="https://rodgert.github.io/2014/12/24/boost-asio-and-zeromq-pt1/" rel="nofollow noreferrer">https://rodgert.github.io/2014/12/24/boost-asio-and-zeromq-pt1/</a>.

Here is the sample code copied from the readme:

<pre><code>#include &lt;azmq/socket.hpp&gt;
#include &lt;boost/asio.hpp&gt;
#include &lt;array&gt;

namespace asio = boost::asio;

int main(int argc, char** argv) {
 asio::io_service ios;
 azmq::sub_socket subscriber(ios);
 subscriber.connect("tcp://192.168.55.112:5556");
 subscriber.connect("tcp://192.168.55.201:7721");
 subscriber.set_option(azmq::socket::subscribe("NASDAQ"));

 azmq::pub_socket publisher(ios);
 publisher.bind("ipc://nasdaq-feed");

 std::array&lt;char, 256&gt; buf;
 for (;;) {
 auto size = subscriber.receive(asio::buffer(buf));
 publisher.send(asio::buffer(buf));
 }
 return 0;
}
</code></pre>

Looks nice. If you try, let me know in the comments if it still works in 2019 [I will probably try in a couple of months and then update this answer] (the repo is stale, last commit was a year ago)

I've got a C++ application that is using ZeroMQ for some messaging. But it also has to provide a SGCI connection for an AJAX / Comet based web service.

For this I need a normal TCP socket. I could do that by normal Posix sockets, but to stay cross platform portable and make my life easier (I hope...) I was thinking of using Boost::ASIO.

But now I have the clash of ZMQ wanting to use it's own <code>zmq_poll()</code> and ASIO it's <code>io_service.run()</code>...

Is there a way to get ASIO to work together with the 0MQ <code>zmq_poll()</code>?

Or is there an other recommended way to achieve such a setup?

Note: I could solve that by using multiple threads - but it's only a little single core / CPU box that'll run that program with a very low amount of SCGI traffic, so multithreading would be a waste of resources...

Using ZeroMQ together with Boost::ASIO

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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