That's theoretically true. But I don't know any public Internet-facing apps that care about that. For non-public networks, sure. For things like TCP-to-RS232 c

That's theoretically true. But I don't know any public Internet-facing apps that care about that. For non-public networks, sure. For things like TCP-to-RS232 connectors that can only service one connection at a time. Happy Eyeballs needs to be disabled for them, but that's just one socket option. And if the Happy Eyeballs protocol was standardized earlier, these kinds of apps arguably would have adapted to it.