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dotancohen01/03/20261 replyview on HN

Correct me if I'm wrong, but UPnP requires my ESP32 to initiate communication. Whereas giving it an IPv6 address would expose it to the entire www even before it attempts communication.


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jech01/03/2026

> Correct me if I'm wrong, but UPnP requires my ESP32 to initiate communication.

Not quite. Using UPnP, any host on your internal network can open a port for any other host. You may be thinking of NAT-PMP.

Additionally, by default UPnP mappings don't expire (unlike NAT-PMP mappings), so if a host crashes with an open port and your ESP32 inherits its IPv4 address, it will be exposed to the Internet.

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