[R] Stream reader/writer API that takes socket stream

[asfimport]

I have been working on Spark integration with Arrow.

I realised that there are no ways to use socket as input to use Arrow stream format. For instance,
I want to something like:

connStream <- socketConnection(port = 9999, blocking = TRUE, open = "wb")

rdf_slices <- # a list of data frames.

stream_writer <- NULL
tryCatch({
  for (rdf_slice in rdf_slices) {
    batch <- record_batch(rdf_slice)
    if (is.null(stream_writer)) {
      stream_writer <- RecordBatchStreamWriter(connStream, batch$schema)  # Here, looks there's no way to use socket.
    }

    stream_writer$write_batch(batch)
  }
},
finally = {
  if (!is.null(stream_writer)) {
    stream_writer$close()
  }
})

Likewise, I cannot find a way to iterate the stream batch by batch

RecordBatchStreamReader(connStream)$batches()  # Here, looks there's no way to use socket.

This looks easily possible in Python side but looks missing in R APIs.

Reporter: Hyukjin Kwon
Assignee: Dewey Dunnington / @paleolimbot

Related issues:

• [R] Support for connection class when reading and writing files (duplicates)

_{Note: This issue was originally created as ARROW-4512. Please see the migration documentation for further details.}

[asfimport]

Wes McKinney / @wesm:
@romainfrancois any thoughts about what might be possible here?

[asfimport]

Dewey Dunnington / @paleolimbot:
See also ARROW-9235!

[asfimport]

Hyukjin Kwon:
Awesome. Feel free to resolve this as a duplicate of ARROW-9235 :-)