diff --git a/html/ndt7-download.js b/html/ndt7-download.js
index 8ab956d9..f115e7e9 100644
--- a/html/ndt7-download.js
+++ b/html/ndt7-download.js
@@ -10,12 +10,12 @@ onmessage = function (ev) {
     postMessage(null)
   }
   sock.onopen = function () {
-    const start = new Date().getTime()
+    const start = performance.now()
     let previous = start
     let total = 0
     sock.onmessage = function (ev) {
       total += (ev.data instanceof Blob) ? ev.data.size : ev.data.length
-      let now = new Date().getTime()
+      let now = performance.now()
       const every = 250  // ms
       if (now - previous > every) {
         postMessage({
diff --git a/html/ndt7-upload.js b/html/ndt7-upload.js
index aa23030f..a24975ff 100644
--- a/html/ndt7-upload.js
+++ b/html/ndt7-upload.js
@@ -11,8 +11,9 @@ onmessage = function (ev) {
     postMessage(null)
   }
   function uploader(socket, data, start, previous, total) {
-    let now = new Date().getTime()
+    let now = performance.now()
     const duration = 10000  // millisecond
+    const every = 250  // millisecond
     if (now - start > duration) {
       sock.close()
       return
@@ -22,11 +23,15 @@ onmessage = function (ev) {
       data = new Uint8Array(data.length * 2) // TODO(bassosimone): fill this message
     }
     const underbuffered = 7 * data.length
-    while (sock.bufferedAmount < underbuffered) {
+    while ((sock.bufferedAmount < underbuffered) &&
+	   (performance.now() - previous < every)) {
       sock.send(data)
       total += data.length
+      if (data.length < maxMessageSize && data.length < (total - sock.bufferedAmount)/16) {
+        break
+      }
     }
-    const every = 250  // millisecond
+    now = performance.now()
     if (now - previous > every) {
       postMessage({
         'AppInfo': {
@@ -42,11 +47,19 @@ onmessage = function (ev) {
       function() { uploader(sock, data, start, previous, total) },
       0)
   }
+  sock.onmessage = function (ev) {
+      if (!(ev.data instanceof Blob)) {
+          let m = JSON.parse(ev.data)
+          m.Origin = 'server'
+          m.Test = 'upload'
+          postMessage(m)
+      }
+  }
   sock.onopen = function () {
     const initialMessageSize = 8192 /* (1<<13) */
     const data = new Uint8Array(initialMessageSize) // TODO(bassosimone): fill this message
     sock.binarytype = 'arraybuffer'
-    const start = new Date().getTime()
+    const start = performance.now()
     uploader(sock, data, start, start, 0)
   }
 }