ERR_EMPTY_RESPONSE Error in html and node.js

I'm a newbie in html and Node.js and trying to upload image to my web app. The problem that I have is it shows me ERR_EMPTY_RESPONSE error after clicking upload button from html.

I think because it is not sending response back from Node.js. So I'm trying to put res.status(501) for error and res.status(200) if it goes through OK.

However, I don't know where I have to put that thing.

Here is my upload button code below,

<form action="/upload", method="post", enctype="multipart/form-data">
  <div style='height:0px; width:0px; overflow:hidden;'><input type="file" name="upFile" id="upFile" onchange="getCmaFileView(this, 'name')" target="dropzone_1"/></div>
   <div style='height:0px; width:0px; overflow:hidden;'><input type="submit" name="Upload" id="Upload" /></div>
</form>

And here is my app.post code from node.js

app.post('/upload', function(req, res, next) {

var form = new multiparty.Form();

      // get field name & value
      form.on('field',function(name,value){
           console.log('normal field / name = '+name+' , value = '+value);
      });

      // file upload handling
      form.on('part',function(part){
           var filename;
           var size;
           if (part.filename) {
                 filename = part.filename;
                 size = part.byteCount;
           }else{
                 part.resume();

           }

           console.log("Write Streaming file :"+global_username);
           var writeStream = fs.createWriteStream('/opt/smarthome/files/'+global_username);
           writeStream.filename = filename;
           part.pipe(writeStream);

           part.on('data',function(chunk){
                 console.log(global_username+'.png'+' read '+chunk.length + 'bytes');
           });

           part.on('end',function(){
                 console.log(global_username+'.png'+' Part read complete');
                 writeStream.end();
           });
      });

      // all uploads are completed
         form.on('close',function(){
         console.log('a');
      });


      // track progress
      form.on('progress',function(byteRead,byteExpected){
           console.log(' Reading total  '+byteRead+'/'+byteExpected);
      });
      form.on('error',function(){
        console.log('error');
        if(err != null){
          res.status(501);
          return;
        } else{
           res.status(200);
        }
      });

      form.parse(req);
});

As you see above Node.js code, I tried to put res.status at the bottom, but it doesn't work and keep showing me ERR_EMPTY_RESPONSE

Am I thinking wrong?? Or is there better way to do this?

Thanks in advance!

via paulc1111