1ZMQ_POLL(3) 0MQ Manual ZMQ_POLL(3)
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6 zmq_poll - input/output multiplexing
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9 int zmq_poll (zmq_pollitem_t *items, int nitems, long timeout);
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12 The zmq_poll() function provides a mechanism for applications to
13 multiplex input/output events in a level-triggered fashion over a set
14 of sockets. Each member of the array pointed to by the items argument
15 is a zmq_pollitem_t structure. The nitems argument specifies the number
16 of items in the items array. The zmq_pollitem_t structure is defined as
17 follows:
18 typedef struct
20 {
21 void *socket;
22 int fd;
23 short events;
24 short revents;
25 } zmq_pollitem_t;
26 For each zmq_pollitem_t item, zmq_poll() shall examine either the 0MQ
28 socket referenced by socket or the standard socket specified by the
29 file descriptor fd, for the event(s) specified in events. If both
30 socket and fd are set in a single zmq_pollitem_t, the 0MQ socket
31 referenced by socket shall take precedence and the value of fd shall be
32 ignored.
33 Note
35 All 0MQ sockets passed to the zmq_poll() function must share the
36 same 0MQ context and must belong to the thread calling zmq_poll().
37 For each zmq_pollitem_t item, zmq_poll() shall first clear the revents
39 member, and then indicate any requested events that have occurred by
40 setting the bit corresponding to the event condition in the revents
41 member.
42 If none of the requested events have occurred on any zmq_pollitem_t
44 item, zmq_poll() shall wait timeout microseconds for an event to occur
45 on any of the requested items. If the value of timeout is 0, zmq_poll()
46 shall return immediately. If the value of timeout is -1, zmq_poll()
47 shall block indefinitely until a requested event has occurred on at
48 least one zmq_pollitem_t.
49 The events and revents members of zmq_pollitem_t are bit masks
51 constructed by OR’ing a combination of the following event flags:
52 ZMQ_POLLIN
54 For 0MQ sockets, at least one message may be received from the
55 socket without blocking. For standard sockets this is equivalent to
56 the POLLIN flag of the poll() system call and generally means that
57 at least one byte of data may be read from fd without blocking.
58 ZMQ_POLLOUT
60 For 0MQ sockets, at least one message may be sent to the socket
61 without blocking. For standard sockets this is equivalent to the
62 POLLOUT flag of the poll() system call and generally means that at
63 least one byte of data may be written to fd without blocking.
64 ZMQ_POLLERR
66 For standard sockets, this flag is passed through zmq_poll() to the
67 underlying poll() system call and generally means that some sort of
68 error condition is present on the socket specified by fd. For 0MQ
69 sockets this flag has no effect if set in events, and shall never
70 be returned in revents by zmq_poll().
71 Note
73 The zmq_poll() function may be implemented or emulated using
74 operating system interfaces other than poll(), and as such may be
75 subject to the limits of those interfaces in ways not defined in
76 this documentation.
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79 Upon successful completion, the zmq_poll() function shall return the
80 number of zmq_pollitem_t structures with events signaled in revents or
81 0 if no events have been signaled. Upon failure, zmq_poll() shall
82 return -1 and set errno to one of the values defined below.
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85 ETERM
86 At least one of the members of the items array refers to a socket
87 whose associated 0MQ context was terminated.
88 EFAULT
90 The provided items was not valid (NULL).
91 EINTR
93 The operation was interrupted by delivery of a signal before any
94 events were available.
95
97 Polling indefinitely for input events on both a 0MQ socket and a
98 standard socket..
99 zmq_pollitem_t items [2];
101 /* First item refers to 0MQ socket 'socket' */
102 items[0].socket = socket;
103 items[0].events = ZMQ_POLLIN;
104 /* Second item refers to standard socket 'fd' */
105 items[1].socket = NULL;
106 items[1].fd = fd;
107 items[1].events = ZMQ_POLLIN;
108 /* Poll for events indefinitely */
109 int rc = zmq_poll (items, 2, -1);
110 assert (rc >= 0);
111 /* Returned events will be stored in items[].revents */
112
115 zmq_socket(3) zmq_send(3) zmq_recv(3) zmq(7)
116 Your operating system documentation for the poll() system call.
118
120 This 0MQ manual page was written by Martin Sustrik
121 <sustrik@250bpm.com[1]> and Martin Lucina <mato@kotelna.sk[2]>.
122
124 1. sustrik@250bpm.com
125 mailto:sustrik@250bpm.com
126 2. mato@kotelna.sk
128 mailto:mato@kotelna.sk
1290MQ 2.1.4 03/30/2011 ZMQ_POLL(3)