# `XGW.DTLS.OtpDemux`
[🔗](https://github.com/Lazarus404/xgw/blob/main/lib/xgw/dtls/otp_demux.ex#L1)

Patches Erlang/OTP's DTLS packet demux so XGW can share one UDP socket.

## Why a patch is needed

Stock OTP DTLS assumes each connection owns a private `:gen_udp` socket.
XGW deliberately multiplexes STUN, DTLS, and SRTP on **one** Listener socket
(standard WebRTC demux). Outbound DTLS must therefore call
`XGW.DTLS.Transport` instead of `:gen_udp.send/4`.

At application start, `patch!/0` loads a drop-in `dtls_packet_demux` BEAM from
XGW's `ebin` when present. If the file is missing, startup continues with
stock OTP (suitable for environments that do not run shared-socket DTLS).

## RFCs

* RFC 7983 -- WebRTC demux model that motivates a shared UDP socket
* RFC 9147 / RFC 6347 -- DTLS (OTP connection that must send on that socket)

# `patch!`

```elixir
@spec patch!() :: :ok
```

Reloads `ebin/dtls_packet_demux.beam` when present.

Always returns `:ok`. Load failures are logged and ignored so the host app
can still boot (for example in test without the patched BEAM).

---

*Consult [api-reference.md](api-reference.md) for complete listing*