Nodejs request socket object parameter - node.js

Question

Sorry if I ask silly question, I am working with the example below regarding on nodejs long polling.
http://www.stoimen.com/blog/2010/12/02/diving-into-node-js-a-long-polling-example/
I understand most of them, but just one thing I am not quite able to understand although I have done thousands of searching.
fs.stat('filepath', function(err, stats) {
// if the file is changed
if (stats.mtime.getTime() > request.socket._idleStart.getTime()) {
// read it
fs.readFile('filepath', 'utf8', function(err, data) {
// return the contents
response.writeHead(200, {
'Content-Type' : 'text/plain',
'Access-Control-Allow-Origin' : '*'
});
// return response
response.write(data, 'utf8');
response.end();
// return
return false;
});
}
});
The part "request.socket._idleStart", what is the meaning of the parameter _idleStart? Actually, I try to print out the whole request object and got the following parameters.
_readableState:
{ highWaterMark: 16384,
buffer: [],
length: 0,
pipes: null,
pipesCount: 0,
flowing: false,
ended: false,
endEmitted: false,
reading: false,
calledRead: false,
sync: true,
needReadable: false,
emittedReadable: false,
readableListening: false,
objectMode: false,
defaultEncoding: 'utf8',
ranOut: false,
awaitDrain: 0,
readingMore: false,
decoder: null,
encoding: null },
readable: true,
domain: null,
_events: {},
_maxListeners: 10,
socket:
....
...
...
I am wondering if there is any documentations describing these parameters, thanks for all for the help!

Answer 1

those parameters with _ underscore, are used for maintaining the state of socket, its not meant for working with them. there are functions that are more reliable than those.
from node.js documentation
readable._read
Note: This function should NOT be called directly. It should be
implemented by child classes, and called by the internal Readable
class methods only.
All Readable stream implementations must provide a _read method to
fetch data from the underlying resource.
This method is prefixed with an underscore because it is internal to
the class that defines it, and should not be called directly by user
programs. However, you are expected to override this method in your
own extension classes.