rzmq (version 0.9.14)

poll.socket: Polls a list of sockets, waiting for the presence of a nonblocking read, write, or error event.

Description

The zmq_poll() function shall poll a list of a sockets for either read, write, or error conditions subject to a millisecond resolution timeout.

Usage

poll.socket(sockets, events, timeout=0L)

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.

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.

Author

ZMQ was written by Martin Sustrik <[e-mail]> and Martin Lucina <[e-mail]>. rzmq was written by Whit Armstrong.

References

http://www.zeromq.org http://api.zeromq.org http://zguide.zeromq.org/page:all

See Also

connect.socket,bind.socket,receive.socket,send.socket,poll.socket

Examples

if (FALSE) {
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)
}