gistfile1.js

var concat = require('concat-stream');
var Hapi = require('hapi');
var multiparty = require('multiparty');
var request = require('request');

var server = new Hapi.server('localhost', 9000);

function createMedia(request, reply) {
  var params = {};
  var form = new multiparty.Form();
  
  // This function is more of a check to see if you've gotten each part stream (files and fields).
  // If everything has been processed then do something with the file stream
  function finishParsing() {
    for (var param in params) {
      if (!params[param]) return; // We're still missing a param so don't finish yet
    }

    // Do fancy stuff
    
    // Prepare form for sending to other server
    var r = request.post('http://<other-super-server>', function (err, res, body) {
      if (err) {
        // handle error
      } else {
        // handle non error
      }
    });
    
    var f = r.form();
    
    // When you don't let hapi parse the form filename and content type headers are directly on the file rather then 
    // in file.hapi. 
    f.append('file', params.file, { filename: params.file.filename, contentType: params.file.headers['content-type']});
    // Append other fields that you want
  }
  
  form.parse(request.payload);
  form.addListener('part', function (part) {
    if (part.name === 'file') {  // This would be whatever the 'file'  stream name is
      params.file = part; // The part is actually a stream so you'd handle that differently than just fields
      finishParsing(); // You don't have to wait for the actual stream to buffer when you dont parse it. 
    } else {
      params[part.name] = false;  // This handles any fields that are sent
      part.pipe(concat({ encoding: 'string', function (data) { // Even the fields are streams so we have to buffer them up to get their values
        params[part.name] = data;
        finishParsing(); // Done processing this field so maybe we're done
      }));
    }
  });
}

server.route({
  method: 'POST',
  path: '/media',
  handler: createMedia,
  config: {
    output: 'stream', // Still want stream objects
    parse: false,    // We don't want Hapi to actually parse the mutltipart stuff and buffer it
    maxBytes: 5368709120
  }
})