Polls a list of sockets, waiting for the presence of a nonblocking read, write, or error event.
poll.socket.RdThe zmq_poll() function shall poll a list of a sockets for either read, write, or error conditions subject to a millisecond resolution timeout.
Arguments
- sockets
a list of zmq socket objects.
- events
a list of character vectors containing one or more events in {read, write, error}. The first element in the list corresponds to the first zmq socket, and so on...
- timeout
the numbers of seconds to wait for events. Fractional seconds are supported. ZeroMQ guarantees at most millisecond resolution. A timeout of -1L blocks until an event occurs; a timeout of 0L is non-blocking.
Value
A list of pairlists corresponding to the polled zmq sockets. Each list has one of more tags from {read, write, error} with logical values indicating the results of the poll operation.
Author
ZMQ was written by Martin Sustrik <sustrik@250bpm.com> and Martin Lucina <mato@kotelna.sk>. rzmq was written by Whit Armstrong.
See also
connect.socket,bind.socket,receive.socket,send.socket,poll.socket
Examples
if (FALSE) { # \dontrun{
library(rzmq)
# Create a set of REP-REQ sockets that
# have a Send, Receive, Send, Receive, ...
# pattern.
context = init.context()
in.socket = init.socket(context,"ZMQ_REP")
bind.socket(in.socket,"tcp://*:5557")
out.socket = init.socket(context,"ZMQ_REQ")
connect.socket(out.socket,"tcp://*:5557")
# Poll the REP and REQ sockets for all events.
events <- poll.socket(list(in.socket, out.socket),
list(c("read", "write", "error"),
c("read", "write", "error")),
timeout=0L)
# The REQ socket is writable without blocking.
paste("Is upstream REP socket readable without blocking?", events[[1]]$read)
paste("Is upstream REP socket writable without blocking?", events[[1]]$write)
paste("Is downstream REQ socket readable without blocking?", events[[2]]$read)
paste("Is downstream REQ socket writable without blocking?", events[[2]]$write)
# Send a message to the REP socket from the REQ socket. The
# REQ socket must respond before the REP socket can send
# another message.
send.socket(out.socket, "Hello World")
events <- poll.socket(list(in.socket, out.socket),
list(c("read", "write", "error"),
c("read", "write", "error")),
timeout=0L)
# The incoming message is readable on the REP socket.
paste("Is upstream REP socket readable without blocking?", events[[1]]$read)
paste("Is upstream REP socket writable without blocking?", events[[1]]$write)
paste("Is downstream REQ socket readable without blocking?", events[[2]]$read)
paste("Is downstream REQ socket writable without blocking?", events[[2]]$write)
receive.socket(in.socket)
events <- poll.socket(list(in.socket, out.socket),
list(c("read", "write", "error"),
c("read", "write", "error")),
timeout=0L)
# The REQ socket is waiting for a response from the REP socket.
paste("Is upstream REP socket readable without blocking?", events[[1]]$read)
paste("Is upstream REP socket writable without blocking?", events[[1]]$write)
paste("Is downstream REQ socket readable without blocking?", events[[2]]$read)
paste("Is downstream REQ socket writable without blocking?", events[[2]]$write)
send.socket(in.socket, "Greetings")
events <- poll.socket(list(in.socket, out.socket),
list(c("read", "write", "error"),
c("read", "write", "error")),
timeout=0L)
# The REP response is waiting to be read on the REQ socket.
paste("Is upstream REP socket readable without blocking?", events[[1]]$read)
paste("Is upstream REP socket writable without blocking?", events[[1]]$write)
paste("Is downstream REQ socket readable without blocking?", events[[2]]$read)
paste("Is downstream REQ socket writable without blocking?", events[[2]]$write)
# Complete the REP-REQ transaction cycle by reading
# the REP response.
receive.socket(out.socket)
} # }