Receive data over a connection (Socket, Context or Stream).
recv(
con,
mode = c("serial", "character", "complex", "double", "integer", "logical", "numeric",
"raw", "string"),
block = NULL,
n = 65536L
)a Socket, Context or Stream.
[default 'serial'] character value or integer equivalent - one
of "serial" (1L), "character" (2L), "complex" (3L), "double" (4L),
"integer" (5L), "logical" (6L), "numeric" (7L), "raw" (8L), or
"string" (9L). The default "serial" means a serialised R object; for
the other modes, received bytes are converted into the respective mode.
"string" is a faster option for length one character vectors. For
Streams, "serial" will default to "character".
[default NULL] which applies the connection default (see
section 'Blocking' below). Specify logical TRUE to block until successful
or FALSE to return immediately even if unsuccessful (e.g. if no
connection is available), or else an integer value specifying the maximum
time to block in milliseconds, after which the operation will time out.
[default 65536L] applicable to Streams only, the maximum number of bytes to receive. Can be an over-estimate, but note that a buffer of this size is reserved.
The received data in the mode specified.
In case of an error, an integer 'errorValue' is returned (to be
distiguishable from an integer message value). This can be verified using
is_error_value().
If an error occurred in unserialization or conversion of the message data to the specified mode, a raw vector will be returned instead to allow recovery (accompanied by a warning).
For Sockets and Contexts: the default behaviour is non-blocking with
block = FALSE. This will return immediately with an error if no messages
are available.
For Streams: the default behaviour is blocking with block = TRUE. This will
wait until a message is received. Set a timeout to ensure that the function
returns under all scenarios. As the underlying implementation uses an
asynchronous receive with a wait, it is recommended to set a small positive
value for block rather than FALSE.
recv_aio() for asynchronous receive.
s1 <- socket("pair", listen = "inproc://nanonext")
s2 <- socket("pair", dial = "inproc://nanonext")
send(s1, data.frame(a = 1, b = 2))
#> [1] 0
res <- recv(s2)
res
#> a b
#> 1 1 2
send(s1, data.frame(a = 1, b = 2))
#> [1] 0
recv(s2)
#> a b
#> 1 1 2
send(s1, c(1.1, 2.2, 3.3), mode = "raw")
#> [1] 0
res <- recv(s2, mode = "double", block = 100)
res
#> [1] 1.1 2.2 3.3
send(s1, "example message", mode = "raw")
#> [1] 0
recv(s2, mode = "character")
#> [1] "example message"
close(s1)
close(s2)
req <- socket("req", listen = "inproc://nanonext")
rep <- socket("rep", dial = "inproc://nanonext")
ctxq <- context(req)
ctxp <- context(rep)
send(ctxq, data.frame(a = 1, b = 2), block = 100)
#> [1] 0
recv(ctxp, block = 100)
#> a b
#> 1 1 2
send(ctxq, c(1.1, 2.2, 3.3), mode = "raw", block = 100)
#> [1] 0
recv(ctxp, mode = "double", block = 100)
#> [1] 1.1 2.2 3.3
close(req)
close(rep)