Write webm blobs / base64 to file via node mediaRecorder - node.js

Question

I'm trying to record a webcam stream via my node server into a new file. To get the webm Blobs I use the mediaRecorder api and then send those via binaryJs to my node server. Then I don't know how to proceed. My current code in node looks like this, but I don't know how to write the chunks to a file:
var binaryServer = require('binaryjs').BinaryServer;
var serverBinaryVideo = binaryServer({port: 9002});
serverBinaryVideo.on('connection', function(client) {
client.on('stream', function(stream, meta) {
stream.on('data', function(chunk) {
console.log(chunk);
});
stream.on('end', function() {
});
});
});
Does it work like this, or should I convert the blob to base64 on my client?
Client Js looks like this for now:
var clientVideo = new BinaryClient('ws://localhost:9002/');
clientVideo.on('open', function() {
// for the sake of this example let's put the stream in the window
window.StreamVideo = clientVideo.createStream();
});
var options = {
audioBitsPerSecond : 128000,
videoBitsPerSecond : 2500000,
mimeType : 'video/webm;codecs=h264' //mp4 not supported in chrome. Original: 'video/webm'
}
var mediaRecorder = new MediaRecorder(audiovideostream, options);
mediaRecorder.start(500); //call every 500ms
mediaRecorder.ondataavailable = function(e) {
// console.log("mediarecorderData");
// console.log(e);
reader.readAsDataURL(e.data);
videoProcess(e.data)
// chunks.push(e.data);
}
mediaRecorder.onerror = function(error) {
console.log(error);
// chunks.push(e.data);
}