pebble send chunk

  // This function sends chunks of data.
  sendChunk = function(start) {
    var txbuf = bytes.slice(start, start + chunkSize);
    console.log("Sending " + txbuf.length + " bytes - starting at offset " + start);
    Pebble.sendAppMessage({ "NETDL_DATA": txbuf },
      function(e) {
        // If there is more data to send - send it.
        if (bytes.length > start + chunkSize) {
          sendChunk(start + chunkSize);
        }
        // Otherwise we are done sending. Send closing message.
        else {
          Pebble.sendAppMessage({"NETDL_END": "done" }, success, failure);
        }
      },
      // Failed to send message - Retry a few times.
      function (e) {
        if (retries++ < 3) {
          console.log("Got a nack for chunk #" + start + " - Retry...");
          sendChunk(start);
        }
        else {
          failure(e);
        }
      }
    );
  };