[英]About ZeroMQ and polling on non-blocking sockets :
In Linux, if an application uses raw non-blocking sockets for reading, in conjunction with poll, will it be possible to be notified when a socket has some data available for reading or not?在 Linux 中,如果应用程序使用原始非阻塞套接字进行读取,结合轮询,是否可以在套接字有一些数据可供读取时得到通知?
I tried to dig into ZeroMQ documentation, but I cannot find my way.我试图深入研究 ZeroMQ 文档,但我找不到我的方法。
I found the flag ZMQ_NOBLOCK
, but it is applied when called zmq_recv
.我找到了标志ZMQ_NOBLOCK
,但它在调用zmq_recv
时被zmq_recv
。
Is there a way to set the socket itself as Non-Blocking so that poll can return immediately if there is nothing to read?有没有办法将套接字本身设置为非阻塞,以便在没有任何内容时轮询可以立即返回?
I am using C++ as language for my app.我使用 C++ 作为我的应用程序的语言。
First, a ZeroMQ- Socket
-instance is not anything like an O/S socket.首先,ZeroMQ- Socket
实例与 O/S 套接字完全不同。 For principal disambiguation, feel free to read posts on conceptual differences.对于主要消歧,请随时阅读有关概念差异的帖子。
This is an often re-articulated misconception, so let me repeat it in bold.这是一个经常被重新阐明的误解,所以让我用粗体重复一遍。
Beware: ZeroMQ Socket()
-instance is not a tcp-socket-as-you-know-it.注意: ZeroMQ Socket()
-instance不是tcp-socket-as-you-know-it。 Best read about the main conceptual differences in [ ZeroMQ hierarchy in less than a five seconds ] or other posts and discussions here关于[主要概念分歧最好看的ZeroMQ层次不到5秒]或其他职位,并在这里讨论
ZMQ_NOBLOCK
symbol can be used in more places: ZMQ_NOBLOCK
符号可以用在更多地方: the zmq_recv()
being one such, zmq_send()
being another. zmq_recv()
是一个, zmq_send()
是另一个。
This symbol is principaly #define
-ed in header file, but somewhere having also some other value-identical aliases, a zmq.DONTWAIT
being one such flag
-composition related symbol for python-wrappers/bindings.这个符号在头文件中主要是#define
-ed,但在某处也有一些其他值相同的别名,一个zmq.DONTWAIT
是 python-wrappers/bindings 的一个这样的flag
相关符号。
Socket
-instance has no such property as (not-)being blocking: Socket
实例没有 (not-) 阻塞这样的属性:this is the core principal miss in your so far posted questions.这是您迄今为止发布的问题中的核心主要失误。
The Socket
-instance does not persist any such feature per-se. Socket
实例本身不保留任何此类功能。
The respective ( individual ) instance operation - a call to a { .recv() | .send() }
相应的(单独的)实例操作 - 调用{ .recv() | .send() }
{ .recv() | .send() }
-method can use a parameter-based mechanism to change it's per-call modus operandi: { .recv() | .send() }
-method 可以使用基于参数的机制来更改其每次调用的操作方式:
flags = { 0, ZMQ_DONTWAIT, ZMQ_SENDMORE, ZMQ_DONTWAIT && ZMQ_SENDMORE }
but having no such option to "turn"-any-such mode on/off to persist. flags = { 0, ZMQ_DONTWAIT, ZMQ_SENDMORE, ZMQ_DONTWAIT && ZMQ_SENDMORE }
但没有这样的选项来“打开”/关闭任何此类模式以保持flags = { 0, ZMQ_DONTWAIT, ZMQ_SENDMORE, ZMQ_DONTWAIT && ZMQ_SENDMORE }
。
Poller.poll()
to return immediately "?问:“有没有办法设置Poller.poll()
立即返回”?
int zmq_poll ( zmq_pollitem_t *items, int nitems,
long timeout
);
int zmq_poll ( zmq_pollitem_t *items, int nitems,
long timeout
);
so,所以,
unless one calls zmq_poll( ..., -1 )
, which turns the polling hang indefinitely long, the zmq_poll()
-call returns as late as timeout
[ms]
, so using timeout == 0
, the zmq_poll()
-call returns immediately, whether there has been found any item or not, that's great , isn't it?除非调用zmq_poll( ..., -1 )
,这会使轮询无限期挂起, zmq_poll()
调用最晚返回timeout
[ms]
,因此使用timeout == 0
, zmq_poll()
调用返回马上,不管有没有发现任何物品,那太好了,不是吗?
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