streamedResponse.js

var filestream = fs.createReadStream(file);
filestream.pipe(res)
  .on("finish", function() {
    log("resource download complete");
  })
  .on("error", function(err) {
    errLog("failure during resource download: %s", err.message);
  });

res
  .on("finish", function() {
    log("response resource download complete");
  })
  .on("error", function(err) {
    errLog("response failure during resource download: %s", err.message);
  });