NN_POLL(3) nanomsg manual NN_POLL(3)NAMEnn_poll - poll a set of SP sockets for readability and/or writability
SYNOPSIS
#include <nanomsg/nn.h>
int nn_poll (struct nn_pollfd *fds, int nfds, int timeout);
DESCRIPTION
The function checks a set of SP socket and reports whether it’s
possible to send a message to the socket and/or receive a message from
each socket.
fds argument is an array of nn_pollfd structures with nfds argument
specifying the size of the array:
struct nn_pollfd {
int fd;
short events;
short revents;
};
Each entry in the array represents an SP socket to check. events field
specifies which events to check for. The value is a bitwise combination
of the following values:
NN_POLLIN
Check whether at least one message can be received from the fd
socket without blocking.
NN_POLLOUT
Check whether at least one message can be sent to the fd socket
without blocking.
After the function returns, revents field contains bitwise combination
of NN_POLLIN and NN_POLLOUT according to whether the socket is readable
or writable.
timeout parameter specifies how long (in milliseconds) should the
function block if there are no events to report.
RETURN VALUE
Upon successful completion, the number of nn_pollfds structures with
events signaled is returned. In case of timeout, return value is 0. In
case of error, -1 is returned and errno is set the one of the values
below.
ERRORS
EBADF
Some of the provided sockets are invalid.
EINTR
The operation was interrupted by delivery of a signal before the
message was sent.
ETERM
The library is terminating.
NOTEnn_poll is a convenience function. You can achieve same behaviour by
using NN_RCVFD and NN_SNDFD socket options. However, using the socket
options allows for usage that’s not possible with nn_poll, such as
simultaneous polling for both SP and OS-level sockets, integration of
SP sockets with external event loops etc.
EXAMPLE
struct nn_pollfd pfd [2];
pfd [0].fd = s1;
pfd [0].events = NN_POLLIN | NN_POLLOUT;
pfd [1].fd = s2;
pfd [1].events = NN_POLLIN;
rc = nn_poll (pfd, 2, 2000);
if (rc == 0) {
printf ("Timeout!");
exit (1);
}
if (rc == -1) {
printf ("Error!");
exit (1);
}
if (pfd [0].revents & NN_POLLIN) {
printf ("Message can be received from s1!");
exit (1);
}
SEE ALSOnn_socket(3)nn_getsockopt(3)nanomsg(7)AUTHORS
Martin Sustrik <sustrik@250bpm.com[1]>
NOTES
1. sustrik@250bpm.com
mailto:sustrik@250bpm.com
nanomsg Unknown 12/23/2015 NN_POLL(3)
