Transport: add MultiTransport to run WT and QUIC concurrently and route sends

server/multi_transport.py

@@ -0,0 +1,26 @@
+from __future__ import annotations
+
+import asyncio
+from .transport import DatagramServerTransport, TransportPeer
+
+
+class MultiTransport(DatagramServerTransport):
+    """Run both WebTransport and QUIC transports and route sends.
+
+    Inbound datagrams share the same on_datagram callback from GameServer,
+    so GameServer sees a unified source of datagrams.
+    """
+
+    def __init__(self, wt_transport: DatagramServerTransport, quic_transport: DatagramServerTransport):
+        self._wt = wt_transport
+        self._quic = quic_transport
+
+    async def send(self, data: bytes, peer: TransportPeer) -> None:
+        # WebTransport peers are tuples (proto, flow_id); QUIC uses protocol instance
+        if isinstance(peer.addr, tuple) and len(peer.addr) == 2:
+            await self._wt.send(data, peer)
+        else:
+            await self._quic.send(data, peer)
+
+    async def run(self) -> None:
+        await asyncio.gather(self._wt.run(), self._quic.run())