private void sendResponse(Status status, String firstBadLink,
String message,
DataOutputStream out)
throws IOException {
Builder builder = BlockOpResponseProto.newBuilder().setStatus(status);
if (firstBadLink != null) {
builder.setFirstBadLink(firstBadLink);
}
if (message != null) {
builder.setMessage(message);
}
builder.build()
.writeDelimitedTo(out);
}