I'm trying to implement a Readable stream that emits objects parsed from UDP
datagrams. I've been looking for some good stream tutorials, but nothing's
really clicking for me. I think this is compounded by the fact that the stream
documentation on nodejs.org says that Readable.push() and Writable._write()
both accept Buffers or strings, not referencing the objets that are implied by
the presence of the objectMode option.
I'm going to be listening on a UDP socket and I want to emit one or more
objects per dgram message; the message is newline delimited and could have
multiple events per message. I then want to use multiple Writable streams to
distribute the received objects. I will not be polling for data, obviously;
there's no read() method appropriate for a datagram. At a high level, I want
to be able to do the following:
var udpListener = new UDPListener(somePort);
var frameHandler = new FrameHandler();
var destination = fs.createWritableStream("targetFile.txt");
udpListener.pipe(frameHandler).pipe(destination);
udpListener should emit objects, frameHandler should be a transformer that
modifies the object, and destination should accept a string or buffer to be
written out to a file or over the network to another service. Under the hood,
UDPListener will create a dgram socket, split received message by newline, turn
the message into an object, and then send it downstream.
The way the documentation for _read reads, it implies that I need to maintain
my own buffer of data received on the UDP socket, which would then be push()'ed
when _read is invoked. I would have thought that I'd just be able to
arbitrarily push() new data, but push()'ing an object results in "[Object
object]" being received at the next phase of the pipeline.
Is an invocation _read() supposed to result in one or more calls to push() by
the implementing class? How do I push() an object?
Thanks,
Brian
--
Brian Lalor
[email protected]
http://github.com/blalor
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