server.js

import { Meteor } from 'meteor/meteor';

WebApp.connectHandlers.use('/file', (req, res) => {
    res.setHeader("Access-Control-Allow-Methods", "PUT");
    res.setHeader("Access-Control-Allow-Origin", "*");
    res.setHeader("Access-Control-Allow-Headers", "Content-Type");

    if (req.method === 'OPTIONS') {
        res.writeHead(200);
        res.end();
        return;
    } else if (req.method === 'PUT') {
        if (!req.headers['content-type'].startsWith('image')) {
            res.writeHead(400);
            res.end();
        }
        
        let getFile = Meteor.wrapAsync(done => {
            let chunks = [];
            req.on('readable', () => {
                chunks.push(req.read());
            });
            req.on('end', () => {
                done(undefined, Buffer.concat(chunks));
            });
        });

        let buffer = getFile();

        res.writeHead(200);
        res.end();
    }
});

`W20170303-13:05:30.830(8)? (STDERR) buffer.js:289
W20170303-13:05:30.834(8)? (STDERR)       length += list[i].length;
W20170303-13:05:30.834(8)? (STDERR)                       
W20170303-13:05:30.835(8)? (STDERR) 
W20170303-13:05:30.835(8)? (STDERR) TypeError: Cannot read property 'length' of null
W20170303-13:05:30.835(8)? (STDERR)     at Function.Buffer.concat (buffer.js:289:24)
W20170303-13:05:30.845(8)? (STDERR)     at IncomingMessage.<anonymous> (server/gcs.js:65:29)
W20170303-13:05:30.846(8)? (STDERR)     at emitNone (events.js:67:13)
W20170303-13:05:30.846(8)? (STDERR)     at IncomingMessage.emit (events.js:166:7)
W20170303-13:05:30.847(8)? (STDERR)     at endReadableNT (_stream_readable.js:923:12)
W20170303-13:05:30.847(8)? (STDERR)     at nextTickCallbackWith2Args (node.js:458:9)
W20170303-13:05:30.847(8)? (STDERR)     at process._tickCallback (node.js:372:17)`

I also have this error. I observed that if the file exceeds at 60kb this error will be thrown