code: function handleServerStreaming(call, handler, metadata) {
    var stream = new ServerWritableStream(call, metadata, handler.serialize);
    stream.waitForCancel();
    var batch = {};
    batch[grpc.opType.RECV_MESSAGE] = true;
    call.startBatch(batch, function(err, result) {
      if (err) {
        stream.emit('error', err);
        return;
      }
      try {
        stream.request = handler.deserialize(result.read);
      } catch (e) {
        e.code = constants.status.INTERNAL;
        stream.emit('error', e);
        return;
      }
      handler.func(stream);
    });
  }
docs: User provided method to handle server streaming methods on the server.
  @callback grpc.Server~handleServerStreamingCall
  @param {grpc~ServerWritableStream} call The call object
   
  Fully handle a server streaming call
  @private
  @param {grpc.internal~Call} call The call to handle
  @param {Object} handler Request handler object for the method that was called
  @param {grpc~Server.handleServerStreamingCall} handler.func The handler
  function
  @param {grpc~deserialize} handler.deserialize The deserialization function
  for request data
  @param {grpc~serialize} handler.serialize The serialization function for
  response data
  @param {grpc.Metadata} metadata Metadata from the client