nanonext (version 0.5.1)

recv: Receive

Description

Receive data over a connection (Socket, Context or Stream).

Usage

recv(
  con,
  mode = c("serial", "character", "complex", "double", "integer", "logical", "numeric",
    "raw"),
  block,
  keep.raw = TRUE,
  ...,
  n = 65536L
)
# S3 method for nanoSocket
recv(
  con,
  mode = c("serial", "character", "complex", "double", "integer", "logical", "numeric",
    "raw"),
  block = FALSE,
  keep.raw = TRUE,
  ...
)
# S3 method for nanoContext
recv(
  con,
  mode = c("serial", "character", "complex", "double", "integer", "logical", "numeric",
    "raw"),
  block = TRUE,
  keep.raw = TRUE,
  ...
)
# S3 method for nanoStream
recv(
  con,
  mode = c("character", "complex", "double", "integer", "logical", "numeric", "raw"),
  block = TRUE,
  keep.raw = TRUE,
  n = 65536L,
  ...
)

Arguments

con

a Socket, Context or Stream.

mode

[default 'serial'] mode of vector to be received - one of 'serial', 'character', 'complex', 'double', 'integer', 'logical', 'numeric', or 'raw'. The default 'serial' means a serialised R object, for the other modes, the raw vector received will be converted into the respective mode. For Streams, 'serial' is not an option and the default is 'character'.

block

logical TRUE to block until successful or FALSE to return immediately even if unsuccessful (e.g. if no messages are available), or else an integer value specifying the maximum time to block in milliseconds, after which the operation will time out.

keep.raw

[default TRUE] logical flag whether to keep the received raw vector (useful for verification e.g. via hashing). If FALSE, will return the converted data only.

...

currently unused.

n

[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.

Value

Named list of 2 elements: 'raw' containing the received raw vector and 'data' containing the converted object, or else the converted object if 'keep.raw' is set to FALSE.

Blocking

For Sockets: the default behaviour is non-blocking with block = FALSE. This will return immediately with an error if no messages are available.

For Contexts and Streams: the default behaviour is blocking with block = TRUE. This will wait until a message is received. Set a timeout in this case to ensure that the function returns under all scenarios. As the underlying implementation uses an asynchronous send with a wait, it is recommended to set a positive integer value for block rather than FALSE.

Details

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 the raw data was successfully received but an error occurred in unserialisation or data conversion (for example if the incorrect mode was specified), the received raw vector will always be returned to allow for the data to be recovered.

Examples

# NOT RUN {
s1 <- socket("pair", listen = "inproc://nanonext")
s2 <- socket("pair", dial = "inproc://nanonext")

send(s1, data.frame(a = 1, b = 2))
res <- recv(s2)
res
send(s1, data.frame(a = 1, b = 2), echo = FALSE)
recv(s2, keep.raw = FALSE)

send(s1, c(1.1, 2.2, 3.3), mode = "raw")
res <- recv(s2, mode = "double", block = 100)
res
send(s1, "example message", mode = "raw", echo = FALSE)
recv(s2, mode = "character", keep.raw = FALSE)

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)
recv(ctxp, block = 100)

send(ctxq, c(1.1, 2.2, 3.3), mode = "raw", block = 100)
recv(ctxp, mode = "double", block = 100)

close(req)
close(rep)

# }