How to set up a proxy server for localhost?

Question

JavaScript

So, there is a server on node js, a middleware that sends data to the client

var taskpath = __dirname + '\\public\\task.json';
console.log(taskpath);
app.post('/task', function(req, res){
  var readable = fs.createReadStream(taskpath);
    readable.pipe(res);
});

I use greasymonkey on the client that handles the request

GM_xmlhttpRequest({
  method: 'POST',
  headers: {
    'Content-Type': 'application/x-www-form-urlencoded'
  },
  url: 'http://localhost:8080/task',
  onload: function(data) {
    var json_text = JSON.stringify(data.response, null, 2),
      your_object = JSON.parse(json_text);
    var href = $('#guide-channels').find('li:contains(' + your_object[0].task[0].channel + ')').find('a').attr('href'),
      videos = 'http://www.youtube.com' + href + '/videos',
      channel = {};
    channel['channel'] = videos;
    /*GM_xmlhttpRequest({
      method: 'POST',
      data: JSON.stringify(channel),
      contentType: 'application/json',
      url: 'http://localhost:8081/getHttp',
      onload: function (xhr) {
        console.log('xhr__', xhr.responseText);
      }
    });*/
  }
});

Everything goes well, but that's when I install the proxy server. gives an error
and before that it gave out like this Please help me, which day I'm struggling with it.