There's something weird going on for certain non-integer values of
argument 'timeout' to base::socketSelect(). For such values, there is
no timeout and you effectively end up with an infinite timeout. I
can reproduce this on R 3.3.1 on Ubuntu 16.04 and RedHat 6.6, but not
on Windows (via Linux Wine).
# 1. In R master session
> con <- socketConnection('localhost', port = 11001, server = TRUE, blocking =
> TRUE, open = 'a+b')
# 2. In R servant session (connect to the above master socket)
> con <- socketConnection('localhost', port = 11001, server = FALSE, blocking =
> TRUE, open = 'a+b')
# 3. In R master session (check if there's something available on connection)
# Wait at most 0 seconds
> t <- system.time(r <- socketSelect(list(con), write = FALSE, timeout = 0));
> print(t); print(r)
user system elapsed
0 0 0
[1] FALSE
# Wait at most 1 seconds
> t <- system.time(r <- socketSelect(list(con), write = FALSE, timeout = 1));
> print(t); print(r)
user system elapsed
0.000 0.000 1.002
[1] FALSE
# Wait at most 2 seconds
> t <- system.time(r <- socketSelect(list(con), write = FALSE, timeout = 2));
> print(t); print(r)
user system elapsed
0.000 0.000 2.002
[1] FALSE
# Wait at most 2.5 seconds
> t <- system.time(r <- socketSelect(list(con), write = FALSE, timeout = 2.5));
> print(t); print(r)
user system elapsed
0.000 0.000 2.502
[1] FALSE
# Wait at most 2.1 seconds
> t <- system.time(r <- socketSelect(list(con), write = FALSE, timeout = 2.1));
> print(t); print(r)
user system elapsed
0.000 0.000 2.101
[1] FALSE
However, here are some weird cases where the value of the 'timeout'
argument is ignored:
# Wait at most 1.9 seconds
> t <- system.time(r <- socketSelect(list(con), write = FALSE, timeout = 1.9));
> print(t); print(r)
^C user system elapsed
3.780 14.888 20.594
> t <- system.time(r <- socketSelect(list(con), write = FALSE, timeout = 0.1));
> print(t); print(r)
^C user system elapsed
2.596 11.208 13.907
[1] FALSE
Note how I had to signal a user interrupt (Ctrl-C) to exit
socketSelect(). Also, not that it still works with the timeout values
chosen above, e.g.
> t <- system.time(r <- socketSelect(list(con), write = FALSE, timeout = 0));
> print(t); print(r)
user system elapsed
0 0 0
[1] FALSE
> t <- system.time(r <- socketSelect(list(con), write = FALSE, timeout = 1));
> print(t); print(r)
user system elapsed
0.000 0.000 1.001
[1] FALSE
> t <- system.time(r <- socketSelect(list(con), write = FALSE, timeout = 2.1));
> print(t); print(r)
user system elapsed
0.000 0.000 2.103
[1] FALSE
It's almost as if there is something special with non-integer values
in (0,2). Not saying these are the only cases, but that's what I've
observed by trial and error. Weird. The fact that it works on
Windows, may suggest it is a Unix specific. Anyway with macOS that
wanna confirm?
/Henrik
Session information details:
# Ubuntu 16.04
> sessionInfo()
R version 3.3.1 (2016-06-21)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Ubuntu 16.04.1 LTS
locale:
[1] LC_CTYPE=en_US.UTF-8 LC_NUMERIC=C
[3] LC_TIME=en_US.UTF-8 LC_COLLATE=en_US.UTF-8
[5] LC_MONETARY=en_US.UTF-8 LC_MESSAGES=en_US.UTF-8
[7] LC_PAPER=en_US.UTF-8 LC_NAME=C
[9] LC_ADDRESS=C LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C
attached base packages:
[1] stats graphics grDevices utils datasets methods base
loaded via a namespace (and not attached):
[1] tools_3.3.1
# RedHat 6.6:
> sessionInfo()
R version 3.3.1 (2016-06-21)
Platform: x86_64-pc-linux-gnu (64-bit)
locale:
[1] C
attached base packages:
[1] stats graphics grDevices utils datasets methods base
loaded via a namespace (and not attached):
[1] tools_3.3.1
# Windows via Wine on Linux
> sessionInfo()
R version 3.3.1 (2016-06-21)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows XP x64 (build 2600) Service Pack 3
locale:
[1] LC_COLLATE=English_United States.1252 LC_CTYPE=English_United States.1252
[3] LC_MONETARY=C LC_NUMERIC=C
[5] LC_TIME=C
attached base packages:
[1] stats graphics grDevices utils datasets methods base
loaded via a namespace (and not attached):
[1] tools_3.3.1
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