nn_poll(3)

1NN_POLL(3)                       nanomsg 1.1.5                      NN_POLL(3)
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NAME

6       nn_poll - poll a set of SP sockets for readability and/or writability
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SYNOPSIS

9       #include <nanomsg/nn.h>
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11       int nn_poll (struct nn_pollfd *fds, int nfds, int timeout);
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DESCRIPTION

14       The function checks a set of SP socket and reports whether it’s
15       possible to send a message to the socket and/or receive a message from
16       each socket.
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18       fds argument is an array of nn_pollfd structures with nfds argument
19       specifying the size of the array:
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21           struct nn_pollfd {
22               int fd;
23               short events;
24               short revents;
25           };
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27       Each entry in the array represents an SP socket to check. events field
28       specifies which events to check for. The value is a bitwise combination
29       of the following values:
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31       NN_POLLIN
32           Check whether at least one message can be received from the fd
33           socket without blocking.
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35       NN_POLLOUT
36           Check whether at least one message can be sent to the fd socket
37           without blocking.
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39       After the function returns, revents field contains bitwise combination
40       of NN_POLLIN and NN_POLLOUT according to whether the socket is readable
41       or writable.
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43       timeout parameter specifies how long (in milliseconds) should the
44       function block if there are no events to report.
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RETURN VALUE

47       Upon successful completion, the number of nn_pollfds structures with
48       events signaled is returned. In case of timeout, return value is 0. In
49       case of error, -1 is returned and errno is set the one of the values
50       below.
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ERRORS

53       EBADF
54           Some of the provided sockets are invalid.
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56       EINTR
57           The operation was interrupted by delivery of a signal before the
58           message was sent.
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60       ETERM
61           The library is terminating.
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NOTE

64       nn_poll is a convenience function. You can achieve same behaviour by
65       using NN_RCVFD and NN_SNDFD socket options. However, using the socket
66       options allows for usage that’s not possible with nn_poll, such as
67       simultaneous polling for both SP and OS-level sockets, integration of
68       SP sockets with external event loops etc.
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EXAMPLE

71           struct nn_pollfd pfd [2];
72           pfd [0].fd = s1;
73           pfd [0].events = NN_POLLIN | NN_POLLOUT;
74           pfd [1].fd = s2;
75           pfd [1].events = NN_POLLIN;
76           rc = nn_poll (pfd, 2, 2000);
77           if (rc == 0) {
78               printf ("Timeout!");
79               exit (1);
80           }
81           if (rc == -1) {
82               printf ("Error!");
83               exit (1);
84           }
85           if (pfd [0].revents & NN_POLLIN) {
86               printf ("Message can be received from s1!");
87               exit (1);
88           }
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AUTHORS

94       Martin Sustrik <sustrik@250bpm.com>
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98                                  2022-01-20                        NN_POLL(3)