Fix WebTransport server implementation and add test client

Server fixes:
- Move H3Connection initialization to ProtocolNegotiated event (matches official aioquic pattern)
- Fix datagram routing to use session_id instead of flow_id
- Add max_datagram_frame_size=65536 to enable QUIC datagrams
- Fix send_datagram() to use keyword arguments
- Add certificate chain handling for Let's Encrypt
- Add no-cache headers to static server

Command-line improvements:
- Move settings from environment variables to argparse
- Add comprehensive CLI arguments with defaults
- Default mode=wt, cert=cert.pem, key=key.pem

Test clients:
- Add test_webtransport_client.py - Python WebTransport client that successfully connects
- Add test_http3.py - Basic HTTP/3 connectivity test

Client updates:
- Auto-configure server URL and certificate hash from /cert-hash.json
- Add ES6 module support

Status:
✅ Python WebTransport client works perfectly
✅ Server properly handles WebTransport connections and datagrams
❌ Chrome fails due to cached QUIC state (QUIC_IETF_GQUIC_ERROR_MISSING)
🔍 Firefox sends packets but fails differently - to be debugged next session

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

.claude/settings.local.json

@@ -0,0 +1,12 @@
+{
+  "permissions": {
+    "allow": [
+      "Read(//g/Coding/code2/**)",
+      "Bash(python -m py_compile server/server.py)",
+      "Bash(node --check client/client.js)",
+      "Bash(node --check client/protocol.js)"
+    ],
+    "deny": [],
+    "ask": []
+  }
+}

CLAUDE.md

@@ -0,0 +1,241 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+This is a real-time multiplayer Snake game using Python 3 (server) and vanilla JavaScript (web client), communicating via WebTransport datagrams (HTTP/3) for low-latency gameplay. The game features continuous persistent gameplay, unique collision mechanics (head-blocks-and-tail-shrinks instead of death), and sophisticated UDP packet handling with compression and partitioning.
+
+## Running the Server
+
+### Dependencies
+```bash
+# Create and activate virtual environment
+python -m venv venv
+source venv/bin/activate  # On Windows: venv\Scripts\activate
+
+# Install dependencies
+pip install -r requirements.txt
+```
+
+### Server Modes
+
+The server supports multiple transport modes via `MODE` environment variable:
+
+```bash
+# In-memory mode (testing, no network)
+MODE=mem python run.py
+
+# WebTransport mode (HTTP/3, default for production)
+MODE=wt QUIC_CERT=cert.pem QUIC_KEY=key.pem python run.py
+
+# QUIC datagram mode only
+MODE=quic QUIC_CERT=cert.pem QUIC_KEY=key.pem python run.py
+
+# Combined mode (both WebTransport and QUIC)
+MODE=net WT_PORT=4433 QUIC_PORT=4443 QUIC_CERT=cert.pem QUIC_KEY=key.pem python run.py
+```
+
+### Environment Variables
+
+- `MODE`: Transport mode (mem|wt|quic|net)
+- `QUIC_CERT` / `QUIC_KEY`: TLS certificate and key paths (required for wt/quic/net)
+- `WT_CERT` / `WT_KEY`: WebTransport-specific cert/key (falls back to QUIC_* if not set)
+- `WT_HOST` / `WT_PORT`: WebTransport server host/port (default: 0.0.0.0:4433)
+- `QUIC_HOST` / `QUIC_PORT`: QUIC server host/port (default: 0.0.0.0:4433, or 4443 in net mode)
+- `STATIC`: Enable static HTTPS server for client (default: 1 in wt mode)
+- `STATIC_HOST` / `STATIC_PORT` / `STATIC_ROOT`: Static server settings (default: same as WT host, port 8443, root "client")
+- `LOG_LEVEL`: Logging level (DEBUG|INFO|WARNING|ERROR)
+- `RUN_SECONDS`: Optional timeout for server shutdown (testing)
+
+### Help
+```bash
+python run.py --help
+```
+
+## Architecture
+
+### Server Architecture (Python 3 + asyncio)
+
+**Core Components:**
+
+1. **server/server.py** (`GameServer`): Authoritative game server
+   - Fixed tick rate simulation (default 10 TPS, configurable 5-30)
+   - Manages player sessions, snakes, apples, collision detection
+   - Handles join/spawn logic, input processing, state broadcasting
+   - Automatically partitions large updates across multiple datagrams (<1200 bytes each to avoid IP fragmentation)
+
+2. **server/model.py**: Game state entities
+   - `GameState`: Field grid, snakes dict, apples list, occupancy map
+   - `Snake`: Deque-based body representation, input buffer (capacity 3), blocked flag
+   - `PlayerSession`: Per-player metadata (id, name, color, peer handle)
+
+3. **server/protocol.py**: Wire protocol implementation
+   - Packet types: JOIN, JOIN_ACK, JOIN_DENY, INPUT, INPUT_BROADCAST, STATE_DELTA, STATE_FULL, PART, CONFIG_UPDATE
+   - TLV body encoding: 2-bit direction streams, RLE compression, chunked variants for oversized snakes
+   - QUIC varint encoding for efficient integer serialization
+   - Sequence number handling with wraparound logic (16-bit)
+
+4. **server/config.py** (`ServerConfig`): Server configuration dataclass with validation
+
+5. **Transport layer** (pluggable):
+   - `server/transport.py`: Abstract `DatagramServerTransport` interface
+   - `server/webtransport_server.py`: WebTransport (HTTP/3) implementation using aioquic
+   - `server/quic_transport.py`: Raw QUIC datagram implementation
+   - `server/multi_transport.py`: Multiplexer for running multiple transports concurrently
+   - `server/static_server.py`: Optional HTTPS static file server for serving client assets
+
+### Client Architecture (Vanilla JavaScript)
+
+**Files:**
+- `client/index.html`: Main HTML page with canvas and UI controls
+- `client/client.js`: Game client, WebTransport connection, input handling, rendering
+- `client/protocol.js`: Wire protocol parsing/building (mirrors server protocol)
+
+**Key Features:**
+- WebTransport datagram API for unreliable, unordered messaging
+- Canvas-based rendering with auto-scaling grid
+- Input buffering (up to 3 direction changes) with 180° turn filtering
+- State update handling: STATE_FULL (initial/recovery), STATE_DELTA (per-tick), PART (fragmented)
+- Packet sequence tracking to discard late/out-of-order updates
+
+### Game Mechanics (Unique Collision System)
+
+**No Death on Collision:**
+- When a snake's head hits an obstacle (wall, self, or another snake), the head stays in place (blocked state)
+- While blocked, the tail shrinks by 1 cell per tick until the player turns to a free direction
+- Minimum length is 1 (head only); snake cannot disappear while player is connected
+
+**Input Buffer Rules:**
+- Client-side buffer holds up to 3 upcoming direction changes
+- Opposite direction to last buffered input replaces the last entry (not appended)
+- Consecutive duplicates are dropped
+- Overflow policy: replace last element
+- Server consumption: At each tick, consume at most one input; skip 180° turns when length > 1
+
+**Apples & Scoring:**
+- Displayed as current snake length (not separate score)
+- Eating an apple grows snake by 1 immediately
+- Target apple count: max(3, min(apples_cap, connected_players × apples_per_snake))
+- When 0 players remain, pre-populate field with exactly 3 apples
+
+**Spawning:**
+- Try to allocate a 3-cell straight strip in a free direction
+- Fallback: spawn length 1 (head only) at any free cell
+- Deny join if no free cells available
+
+### Protocol Details
+
+**Packet Structure:**
+```
+Header (all packets):
+  ver (u8) | type (u8) | flags (u8) | seq (u16 big-endian) | [tick (u16 optional)]
+```
+
+**Sequence Numbers:**
+- 16-bit wraparound with half-range window comparison: `is_newer(a,b) = ((a-b) & 0xFFFF) < 0x8000`
+- Clients discard packets with older seq than last applied per sender
+
+**State Encoding:**
+- **STATE_FULL**: Complete snapshot (on join, periodic recovery); includes all snakes + apples
+  - Per-snake: id (u8), len (u16), head (x,y), body TLV (BODY_2BIT or BODY_RLE)
+- **STATE_DELTA**: Incremental update (per tick); includes only changed snakes + apple diffs
+  - Per-change: snake_id, flags (head_moved|tail_removed|grew|blocked), direction, new_head coords
+- **PART**: Multi-part fragmentation for large updates (>1200 bytes)
+  - Fields: update_id (u16), part_index, parts_total, inner_type (STATE_FULL or STATE_DELTA), chunk_payload
+
+**Body TLV Types:**
+- `BODY_2BIT (0x00)`: 2-bit direction stream (up=00, right=01, down=10, left=11), packed LSB-first
+- `BODY_RLE (0x01)`: Run-length encoding (dir u8, count QUIC varint) for straight segments
+- `BODY_2BIT_CHUNK (0x10)` / `BODY_RLE_CHUNK (0x11)`: Chunked variants for splitting oversized snakes across parts
+  - Chunk header: start_index (u16), dirs_in_chunk (u16)
+
+**Input Broadcasting:**
+- Server relays client inputs immediately to all other clients as INPUT_BROADCAST packets
+- Enables client-side opponent prediction during late/lost state updates
+- Fields: player_id, input_seq, base_tick, events (rel_tick_offset + direction), optional apply_at_tick
+
+**Partitioning Strategy:**
+- Soft limit: 1200 bytes per datagram (avoid fragmentation; MTU ~1280-1500)
+- Whole-snake-first: pack complete snakes greedily; if a single snake exceeds budget, split using chunked TLV
+- Apples included only in first part; clients merge across parts using update_id
+
+## Key Simulation Details
+
+**Tick Order:**
+1. Consume at most one valid input per snake (apply 180° rule for length > 1)
+2. Compute intended head step; if blocked (wall/occupied), set `blocked=True` and keep head stationary
+3. If blocked: shrink tail by 1 (min length 1)
+4. If moving into apple: grow by 1 (don't shrink tail that tick) and respawn apple
+5. Emit per-snake delta and global apple changes
+
+**Collision Detection:**
+- Occupancy map tracks all snake cells as (coord) -> (snake_id, index)
+- Allow moving into own tail if it will vacate (i.e., not growing)
+- Walls block only when `wrap_edges=False`; wrapped coordinates computed by `_step_from()`
+
+**180° Turn Handling:**
+- Checked at consumption time using XOR: `(int(new_dir) ^ int(current_dir)) == 2`
+- Allowed only when snake length == 1 (head only)
+
+## Development Notes
+
+- **Testing**: No automated test suite currently exists. Manual testing via in-memory mode (`MODE=mem`) or live WebTransport server.
+- **Logging**: Use `LOG_LEVEL=DEBUG` for verbose packet-level debugging.
+- **Field Size**: Default 60×40; protocol supports 3×3 to 255×255 (negotiated in JOIN_ACK).
+- **Players**: Max 32 concurrent (ids 0-31); names truncated to 16 UTF-8 bytes.
+- **Colors**: 32-color palette; deterministic mapping from player_id to color_id (0-31).
+- **Tick Rate Changes**: Server broadcasts CONFIG_UPDATE every 50 ticks; clients apply at next tick boundary.
+- **Compression**: Optional global DEFLATE mode (handshake-only; requires server restart). Currently defaults to "none".
+- **Browser Compatibility**: Requires WebTransport API support (latest Firefox/Chrome).
+
+## Common Patterns
+
+**Adding a New Packet Type:**
+1. Add enum value to `PacketType` in server/protocol.py and client/protocol.js
+2. Implement builder function in protocol (e.g., `build_foo()`) and parser (e.g., `parse_foo()`)
+3. Handle in server's `on_datagram()` and client's `readLoop()` switch statements
+4. Update header packing if tick field is required (pass tick to `pack_header()`)
+
+**Modifying Simulation Logic:**
+1. Edit `_simulate_tick()` in server/server.py for per-tick updates
+2. Update `SnakeDelta` dataclass if new change types are needed
+3. Adjust `build_state_delta_body()` if encoding changes
+4. Mirror changes in client rendering logic (client/client.js)
+
+**Changing Configuration:**
+1. Update `ServerConfig` dataclass in server/config.py
+2. Add runtime validation in `validate_runtime()`
+3. If live-configurable: broadcast via CONFIG_UPDATE packet; otherwise require server restart
+4. Update JOIN_ACK builder/parser if part of handshake
+
+## File Organization
+
+```
+G:\Coding\code2\
+├── run.py                  # Server entrypoint with mode switching
+├── requirements.txt        # Python dependencies (aioquic, cryptography)
+├── PROJECT_PLAN.md         # Detailed design spec (authoritative reference)
+├── IDEAS.md                # Original feature brainstorming
+├── server/
+│   ├── server.py           # GameServer (tick loop, join/spawn, simulation)
+│   ├── model.py            # GameState, Snake, PlayerSession entities
+│   ├── protocol.py         # Wire protocol (packet builders/parsers, TLV encoding)
+│   ├── config.py           # ServerConfig dataclass
+│   ├── transport.py        # Abstract DatagramServerTransport interface
+│   ├── webtransport_server.py  # HTTP/3 WebTransport implementation
+│   ├── quic_transport.py   # QUIC datagram implementation
+│   ├── multi_transport.py  # Multi-transport multiplexer
+│   ├── static_server.py    # Optional HTTPS static file server
+│   └── utils.py            # Utility functions
+└── client/
+    ├── index.html          # Main HTML page
+    ├── client.js           # Game client (WebTransport, input, rendering)
+    └── protocol.js         # Wire protocol (mirrors server protocol.py)
+```
+
+## References
+
+- **PROJECT_PLAN.md**: Comprehensive design document covering protocol, mechanics, limits, testing strategy, and milestones.
+- **aioquic**: Python QUIC and HTTP/3 library (https://github.com/aiortc/aioquic)
+- **WebTransport**: W3C spec for low-latency client-server messaging over QUIC (https://w3c.github.io/webtransport/)

client/client.js

@@ -1,4 +1,4 @@
-import { PacketType, Direction, packHeader, parseHeader, buildJoin, buildInput, parseJoinAck, parseStateFullBody } from './protocol.js';
+import { PacketType, Direction, packHeader, parseHeader, buildJoin, buildInput, parseJoinAck, parseStateFullBody, parseStateDeltaBody } from './protocol.js';
 
 const ui = {
   url: document.getElementById('url'),
@@ -109,7 +109,79 @@ async function readLoop() {
           break;
         }
         case PacketType.STATE_DELTA: {
-          // Minimal: ignore detailed deltas for now; rely on periodic full (good enough for a demo)
+          const delta = parseStateDeltaBody(dv, off);
+          // Apply changes to local snake state
+          for (const ch of delta.changes) {
+            let snake = snakes.get(ch.snakeId);
+            if (!snake) {
+              // New snake appeared; skip for now (will get it in next full update)
+              continue;
+            }
+
+            // Update direction (always present)
+            // Note: direction is the current direction, not necessarily the new head direction
+
+            if (ch.headMoved) {
+              // Snake moved: prepend new head position
+              // Compute direction from old head to new head
+              const oldHx = snake.hx;
+              const oldHy = snake.hy;
+              const newHx = ch.newHeadX;
+              const newHy = ch.newHeadY;
+
+              // Determine direction of movement
+              let moveDir = ch.direction;
+              if (newHx === oldHx && newHy === oldHy - 1) moveDir = Direction.UP;
+              else if (newHx === oldHx + 1 && newHy === oldHy) moveDir = Direction.RIGHT;
+              else if (newHx === oldHx && newHy === oldHy + 1) moveDir = Direction.DOWN;
+              else if (newHx === oldHx - 1 && newHy === oldHy) moveDir = Direction.LEFT;
+
+              // Update head position
+              snake.hx = newHx;
+              snake.hy = newHy;
+
+              // If tail was removed (normal move), keep dirs same length by prepending new dir
+              // If grew (ate apple), prepend without removing tail
+              if (ch.grew) {
+                // Growing: add direction to front, don't remove from back
+                snake.dirs = [moveDir, ...snake.dirs];
+                snake.len += 1;
+              } else if (ch.tailRemoved) {
+                // Normal move: head advances, tail shrinks
+                // Keep dirs array same size (represents len-1 directions)
+                // Actually, we need to be careful here about the representation
+                // dirs[i] tells us how to get from cell i to cell i+1
+                // When head moves and tail shrinks, we add new dir at front, remove old from back
+                if (snake.dirs.length > 0) {
+                  snake.dirs.pop(); // remove tail direction
+                }
+                snake.dirs = [moveDir, ...snake.dirs];
+              } else {
+                // Head moved but tail didn't remove (shouldn't happen in normal gameplay)
+                snake.dirs = [moveDir, ...snake.dirs];
+                snake.len += 1;
+              }
+            } else if (ch.blocked) {
+              // Snake is blocked: head stayed in place, tail shrunk
+              if (ch.tailRemoved && snake.dirs.length > 0) {
+                snake.dirs.pop(); // remove last direction (tail shrinks)
+                snake.len = Math.max(1, snake.len - 1);
+              }
+            }
+          }
+
+          // Apply apple changes
+          const appleSet = new Set(apples.map(a => `${a[0]},${a[1]}`));
+          for (const [x, y] of delta.applesAdded) {
+            appleSet.add(`${x},${y}`);
+          }
+          for (const [x, y] of delta.applesRemoved) {
+            appleSet.delete(`${x},${y}`);
+          }
+          apples = Array.from(appleSet).map(s => {
+            const [x, y] = s.split(',').map(Number);
+            return [x, y];
+          });
           break;
         }
         default: break;
@@ -121,24 +193,61 @@ async function readLoop() {
 }
 
 async function connectWT() {
+  // Check if WebTransport is available
+  if (typeof WebTransport === 'undefined') {
+    setStatus('ERROR: WebTransport not supported in this browser. Use Chrome/Edge 97+ or Firefox with flag enabled.');
+    return;
+  }
+
   const url = ui.url.value.trim();
   const hashHex = ui.hash.value.trim();
+
+  if (!url) {
+    setStatus('ERROR: Please enter a server URL');
+    return;
+  }
+
   setStatus('connecting...');
+  console.log('Connecting to:', url);
+
   const opts = {};
   if (hashHex) {
-    const bytes = new Uint8Array(hashHex.match(/.{1,2}/g).map(b => parseInt(b,16)));
+    try {
-    opts.serverCertificateHashes = [{ algorithm: 'sha-256', value: bytes }];
+      const bytes = new Uint8Array(hashHex.match(/.{1,2}/g).map(b => parseInt(b,16)));
+      opts.serverCertificateHashes = [{ algorithm: 'sha-256', value: bytes }];
+      console.log('Using certificate hash:', hashHex);
+    } catch (err) {
+      setStatus('ERROR: Invalid certificate hash format');
+      return;
+    }
+  } else {
+    console.warn('No certificate hash provided - connection may fail for self-signed certs');
+  }
+
+  try {
+    const wt = new WebTransport(url, opts);
+    await wt.ready;
+    transport = wt;
+    writer = wt.datagrams.writable.getWriter();
+    setStatus('connected to server');
+    console.log('WebTransport connected successfully');
+
+    readLoop();
+    requestAnimationFrame(render);
+
+    // Send JOIN immediately (spectator → player upon space handled below)
+    const pkt = buildJoin(1, nextSeq(), ui.name.value.trim());
+    await writer.write(pkt);
+  } catch (err) {
+    console.error('WebTransport connection failed:', err);
+    if (err.message.includes('certificate')) {
+      setStatus('ERROR: Certificate validation failed. Check cert hash or use valid CA cert.');
+    } else if (err.message.includes('net::')) {
+      setStatus('ERROR: Network error - is server running on ' + url + '?');
+    } else {
+      setStatus('ERROR: ' + err.message);
+    }
   }
-  const wt = new WebTransport(url, opts);
-  await wt.ready;
-  transport = wt;
-  writer = wt.datagrams.writable.getWriter();
-  setStatus('connected');
-  readLoop();
-  requestAnimationFrame(render);
-  // Send JOIN immediately (spectator → player upon space handled below)
-  const pkt = buildJoin(1, nextSeq(), ui.name.value.trim());
-  await writer.write(pkt);
 }
 
 function dirFromKey(e) {
@@ -157,7 +266,47 @@ async function onKey(e) {
   try { await writer.write(pkt); } catch (err) { /* ignore */ }
 }
 
+// Auto-configure on page load
+async function autoConfigureFromServer() {
+  try {
+    // Try to fetch cert hash from the static server
+    const response = await fetch('/cert-hash.json');
+    if (!response.ok) {
+      setStatus('Auto-config unavailable, please enter manually');
+      return;
+    }
+    const config = await response.json();
+
+    // Auto-populate fields
+    if (config.wtUrl) {
+      // Use the hostname from browser but with the WT port from server
+      const hostname = window.location.hostname || '127.0.0.1';
+      const wtPort = config.wtPort || 4433;
+      ui.url.value = `https://${hostname}:${wtPort}/`;
+    }
+    if (config.sha256) {
+      ui.hash.value = config.sha256;
+    }
+
+    setStatus('Auto-configured from server');
+    console.log('Auto-configured:', config);
+  } catch (err) {
+    console.warn('Auto-config failed:', err);
+    // Fallback: just populate URL from browser location
+    const hostname = window.location.hostname || '127.0.0.1';
+    ui.url.value = `https://${hostname}:4433/`;
+    setStatus('Manual configuration required');
+  }
+}
+
 ui.connect.onclick = () => { connectWT().catch(e => setStatus('connect failed: ' + e)); };
 window.addEventListener('keydown', onKey);
 window.addEventListener('resize', render);
 
+// Auto-configure when page loads
+if (document.readyState === 'loading') {
+  document.addEventListener('DOMContentLoaded', autoConfigureFromServer);
+} else {
+  autoConfigureFromServer();
+}
+

client/index.html

@@ -15,16 +15,15 @@
   </head>
   <body>
     <div id="ui">
-      <label>Server URL (WebTransport): <input id="url" value="https://localhost:4433/"/></label>
+      <label>Server URL (WebTransport): <input id="url" value="https://localhost:4433/" placeholder="Auto-configured..."/></label>
-      <label>SHA-256 Cert Hash (hex, optional for self-signed): <input id="hash" placeholder="e.g., aabbcc..."/></label>
+      <label>Certificate Hash (SHA-256, auto-configured): <input id="hash" placeholder="Auto-configured from server..."/></label>
       <label>Name: <input id="name" value="guest"/></label>
       <button id="connect">Connect</button>
       <span id="status"></span>
     </div>
     <div id="overlay">press space to join</div>
     <canvas id="view"></canvas>
-    <script src="protocol.js"></script>
+    <script type="module" src="client.js"></script>
-    <script src="client.js"></script>
   </body>
   </html>
 

client/protocol.js

@@ -158,3 +158,57 @@ export function parseStateFullBody(dv, off) {
   return { snakes, apples, off };
 }
 
+export function parseStateDeltaBody(dv, off) {
+  // Parse STATE_DELTA body format (mirrors server/protocol.py build_state_delta_body)
+  // update_id (u16)
+  const updateId = dv.getUint16(off); off += 2;
+
+  // changes count (QUIC varint)
+  let [changesCount, p1] = quicVarintDecode(dv, off); off = p1;
+
+  const changes = [];
+  for (let i = 0; i < changesCount; i++) {
+    const snakeId = dv.getUint8(off); off += 1;
+    const flags = dv.getUint8(off); off += 1;
+    const direction = dv.getUint8(off) & 0x03; off += 1;
+
+    const headMoved = (flags & 0x01) !== 0;
+    const tailRemoved = (flags & 0x02) !== 0;
+    const grew = (flags & 0x04) !== 0;
+    const blocked = (flags & 0x08) !== 0;
+
+    let newHeadX = 0, newHeadY = 0;
+    if (headMoved) {
+      newHeadX = dv.getUint8(off); off += 1;
+      newHeadY = dv.getUint8(off); off += 1;
+    }
+
+    changes.push({
+      snakeId,
+      headMoved,
+      tailRemoved,
+      grew,
+      blocked,
+      direction,
+      newHeadX,
+      newHeadY
+    });
+  }
+
+  // apples added (count + coords)
+  let [applesAddedCount, p2] = quicVarintDecode(dv, off); off = p2;
+  const applesAdded = [];
+  for (let i = 0; i < applesAddedCount; i++) {
+    applesAdded.push([dv.getUint8(off++), dv.getUint8(off++)]);
+  }
+
+  // apples removed (count + coords)
+  let [applesRemovedCount, p3] = quicVarintDecode(dv, off); off = p3;
+  const applesRemoved = [];
+  for (let i = 0; i < applesRemovedCount; i++) {
+    applesRemoved.push([dv.getUint8(off++), dv.getUint8(off++)]);
+  }
+
+  return { updateId, changes, applesAdded, applesRemoved, off };
+}
+

run.py

@@ -1,5 +1,5 @@
 import asyncio
-import os
+import argparse
 import logging
 import sys
 
@@ -7,109 +7,332 @@ from server.server import GameServer
 from server.config import ServerConfig
 
 
-async def _run_tasks_with_optional_timeout(tasks):
+async def _run_tasks_with_optional_timeout(tasks, timeout_s=None):
-    """Await tasks, optionally honoring RUN_SECONDS env var to cancel after a timeout."""
+    """Await tasks, optionally with a timeout to cancel after specified seconds."""
-    timeout_s = os.environ.get("RUN_SECONDS")
     if not timeout_s:
         await asyncio.gather(*tasks)
         return
     try:
         await asyncio.wait_for(asyncio.gather(*tasks), timeout=float(timeout_s))
     except asyncio.TimeoutError:
-        logging.info("Timeout reached (RUN_SECONDS=%s); stopping server tasks...", timeout_s)
+        logging.info("Timeout reached (%s seconds); stopping server tasks...", timeout_s)
         for t in tasks:
             t.cancel()
         await asyncio.gather(*tasks, return_exceptions=True)
 
 
-async def run_in_memory():
+async def run_in_memory(args):
     from server.transport import InMemoryTransport
-    cfg = ServerConfig()
+    cfg = ServerConfig(
+        width=args.width,
+        height=args.height,
+        tick_rate=args.tick_rate,
+        wrap_edges=args.wrap_edges,
+        apples_per_snake=args.apples_per_snake,
+        apples_cap=args.apples_cap,
+        players_max=args.players_max,
+    )
     server = GameServer(transport=InMemoryTransport(lambda d, p: server.on_datagram(d, p)), config=cfg)
     tasks = [asyncio.create_task(server.transport.run()), asyncio.create_task(server.tick_loop())]
-    await _run_tasks_with_optional_timeout(tasks)
+    await _run_tasks_with_optional_timeout(tasks, args.run_seconds)
 
 
-async def run_quic():
+async def run_quic(args):
+    import os
     from server.quic_transport import QuicWebTransportServer
-    cfg = ServerConfig()
+    from server.utils import combine_cert_chain
-    host = os.environ.get("QUIC_HOST", "0.0.0.0")
-    port = int(os.environ.get("QUIC_PORT", "4433"))
-    cert = os.environ["QUIC_CERT"]
-    key = os.environ["QUIC_KEY"]
-    server = GameServer(transport=QuicWebTransportServer(host, port, cert, key, lambda d, p: server.on_datagram(d, p)), config=cfg)
-    tasks = [asyncio.create_task(server.transport.run()), asyncio.create_task(server.tick_loop())]
-    await _run_tasks_with_optional_timeout(tasks)
 
+    cfg = ServerConfig(
+        width=args.width,
+        height=args.height,
+        tick_rate=args.tick_rate,
+        wrap_edges=args.wrap_edges,
+        apples_per_snake=args.apples_per_snake,
+        apples_cap=args.apples_cap,
+        players_max=args.players_max,
+    )
 
-async def run_webtransport():
+    # Handle certificate chain
-    from server.webtransport_server import WebTransportServer
+    # Check if cert file contains multiple certificates (like Let's Encrypt fullchain.pem)
-    from server.static_server import start_https_static
+    with open(args.cert, 'r') as f:
-    cfg = ServerConfig()
+        cert_content = f.read()
-    host = os.environ.get("WT_HOST", os.environ.get("QUIC_HOST", "0.0.0.0"))
+
-    port = int(os.environ.get("WT_PORT", os.environ.get("QUIC_PORT", "4433")))
+    from server.utils import split_pem_certificates
-    cert = os.environ.get("WT_CERT") or os.environ["QUIC_CERT"]
+    certs_in_file = split_pem_certificates(cert_content)
-    key = os.environ.get("WT_KEY") or os.environ["QUIC_KEY"]
+
-    # Optional static HTTPS server for client assets
+    cert_file = args.cert
-    static = os.environ.get("STATIC", "1")
+    temp_cert_file = None
-    static_host = os.environ.get("STATIC_HOST", host)
+
-    static_port = int(os.environ.get("STATIC_PORT", "8443"))
+    if args.cert_chain:
-    static_root = os.environ.get("STATIC_ROOT", "client")
+        # Combine cert + chain files into single file
-    httpd = None
+        temp_cert_file = combine_cert_chain(args.cert, args.cert_chain)
-    if static == "1":
+        cert_file = temp_cert_file
-        httpd, _t = start_https_static(static_host, static_port, cert, key, static_root)
+        logging.info("Combined certificate with %d chain file(s)", len(args.cert_chain))
-        print(f"HTTPS static server: https://{static_host}:{static_port}/ serving '{static_root}'")
+    elif len(certs_in_file) > 1:
-    server = GameServer(transport=WebTransportServer(host, port, cert, key, lambda d, p: server.on_datagram(d, p)), config=cfg)
+        # Certificate file contains full chain - reformat it for aioquic
-    print(f"WebTransport server: https://{host}:{port}/ (HTTP/3)")
+        temp_cert_file = combine_cert_chain(args.cert, [])
+        cert_file = temp_cert_file
+        logging.info("Reformatted certificate chain from fullchain file (%d certs)", len(certs_in_file))
+
+    server = GameServer(transport=QuicWebTransportServer(args.quic_host, args.quic_port, cert_file, args.key, lambda d, p: server.on_datagram(d, p)), config=cfg)
+    logging.info("QUIC server: %s:%d", args.quic_host, args.quic_port)
     try:
         tasks = [asyncio.create_task(server.transport.run()), asyncio.create_task(server.tick_loop())]
-        await _run_tasks_with_optional_timeout(tasks)
+        await _run_tasks_with_optional_timeout(tasks, args.run_seconds)
+    finally:
+        if temp_cert_file:
+            os.unlink(temp_cert_file)  # Clean up temp combined cert file
+
+
+async def run_webtransport(args):
+    import json
+    import os
+    from server.webtransport_server import WebTransportServer
+    from server.static_server import start_https_static
+    from server.utils import get_cert_sha256_hash, combine_cert_chain, extract_server_cert
+
+    cfg = ServerConfig(
+        width=args.width,
+        height=args.height,
+        tick_rate=args.tick_rate,
+        wrap_edges=args.wrap_edges,
+        apples_per_snake=args.apples_per_snake,
+        apples_cap=args.apples_cap,
+        players_max=args.players_max,
+    )
+
+    # Handle certificate chain
+    # Check if cert file contains multiple certificates (like Let's Encrypt fullchain.pem)
+    with open(args.cert, 'r') as f:
+        cert_content = f.read()
+
+    from server.utils import split_pem_certificates
+    certs_in_file = split_pem_certificates(cert_content)
+
+    cert_file = args.cert
+    temp_cert_file = None
+
+    if args.cert_chain:
+        # Combine cert + chain files into single file
+        temp_cert_file = combine_cert_chain(args.cert, args.cert_chain)
+        cert_file = temp_cert_file
+        logging.info("Combined certificate with %d chain file(s)", len(args.cert_chain))
+    elif len(certs_in_file) > 1:
+        # Certificate file contains full chain - reformat it for aioquic
+        temp_cert_file = combine_cert_chain(args.cert, [])
+        cert_file = temp_cert_file
+        logging.info("Reformatted certificate chain from fullchain file (%d certs)", len(certs_in_file))
+
+    # Calculate certificate hash for WebTransport client (only hash server cert, not chain)
+    server_cert_file = extract_server_cert(args.cert)
+    cert_hash = get_cert_sha256_hash(server_cert_file)
+    if server_cert_file != args.cert:
+        os.unlink(server_cert_file)  # Clean up temp file
+
+    # Prepare cert-hash.json content
+    cert_hash_json = json.dumps({
+        "sha256": cert_hash,
+        "wtUrl": f"https://{args.wt_host}:{args.wt_port}/",
+        "wtPort": args.wt_port
+    })
+
+    # Optional static HTTPS server for client assets
+    httpd = None
+    if args.static:
+        httpd, _t = start_https_static(
+            args.static_host,
+            args.static_port,
+            cert_file,
+            args.key,
+            args.static_root,
+            cert_hash_json=cert_hash_json
+        )
+        print(f"HTTPS static server: https://{args.static_host}:{args.static_port}/ serving '{args.static_root}'")
+        print(f"Certificate SHA-256: {cert_hash}")
+
+    server = GameServer(transport=WebTransportServer(args.wt_host, args.wt_port, cert_file, args.key, lambda d, p: server.on_datagram(d, p)), config=cfg)
+    print(f"WebTransport server: https://{args.wt_host}:{args.wt_port}/ (HTTP/3)")
+    try:
+        tasks = [asyncio.create_task(server.transport.run()), asyncio.create_task(server.tick_loop())]
+        await _run_tasks_with_optional_timeout(tasks, args.run_seconds)
     finally:
         if httpd is not None:
             httpd.shutdown()
+        if temp_cert_file:
+            os.unlink(temp_cert_file)  # Clean up temp combined cert file
+
+
+async def run_net(args):
+    import os
+    from server.webtransport_server import WebTransportServer
+    from server.quic_transport import QuicWebTransportServer
+    from server.multi_transport import MultiTransport
+    from server.utils import combine_cert_chain
+
+    cfg = ServerConfig(
+        width=args.width,
+        height=args.height,
+        tick_rate=args.tick_rate,
+        wrap_edges=args.wrap_edges,
+        apples_per_snake=args.apples_per_snake,
+        apples_cap=args.apples_cap,
+        players_max=args.players_max,
+    )
+
+    # Handle certificate chain
+    # Check if cert file contains multiple certificates (like Let's Encrypt fullchain.pem)
+    with open(args.cert, 'r') as f:
+        cert_content = f.read()
+
+    from server.utils import split_pem_certificates
+    certs_in_file = split_pem_certificates(cert_content)
+
+    cert_file = args.cert
+    temp_cert_file = None
+
+    if args.cert_chain:
+        # Combine cert + chain files into single file
+        temp_cert_file = combine_cert_chain(args.cert, args.cert_chain)
+        cert_file = temp_cert_file
+        logging.info("Combined certificate with %d chain file(s)", len(args.cert_chain))
+    elif len(certs_in_file) > 1:
+        # Certificate file contains full chain - reformat it for aioquic
+        temp_cert_file = combine_cert_chain(args.cert, [])
+        cert_file = temp_cert_file
+        logging.info("Reformatted certificate chain from fullchain file (%d certs)", len(certs_in_file))
+
+    server: GameServer
+    wt = WebTransportServer(args.wt_host, args.wt_port, cert_file, args.key, lambda d, p: server.on_datagram(d, p))
+    qu = QuicWebTransportServer(args.quic_host, args.quic_port, cert_file, args.key, lambda d, p: server.on_datagram(d, p))
+    m = MultiTransport(wt, qu)
+    server = GameServer(transport=m, config=cfg)
+    logging.info("WebTransport server: %s:%d", args.wt_host, args.wt_port)
+    logging.info("QUIC server: %s:%d", args.quic_host, args.quic_port)
+    try:
+        tasks = [asyncio.create_task(m.run()), asyncio.create_task(server.tick_loop())]
+        await _run_tasks_with_optional_timeout(tasks, args.run_seconds)
+    finally:
+        if temp_cert_file:
+            os.unlink(temp_cert_file)  # Clean up temp combined cert file
+
+
+def parse_args():
+    parser = argparse.ArgumentParser(
+        description="Real-time multiplayer Snake game server",
+        formatter_class=argparse.RawDescriptionHelpFormatter,
+        epilog="""
+Examples:
+  python run.py                                    # WebTransport mode with defaults
+  python run.py --mode mem                         # In-memory mode (testing)
+  python run.py --mode quic --quic-port 5000       # QUIC mode on custom port
+  python run.py --cert my.pem --key my.key         # Custom TLS certificate
+  python run.py --no-static                        # Disable static HTTPS server
+  python run.py --width 80 --height 60             # Custom field size
+        """
+    )
+
+    # Transport mode
+    parser.add_argument("--mode", choices=["mem", "wt", "quic", "net"], default="wt",
+                        help="Transport mode: mem (in-memory), wt (WebTransport/HTTP3), quic (QUIC datagrams), net (both wt+quic). Default: wt")
+
+    # TLS certificate/key
+    parser.add_argument("--cert", default="cert.pem",
+                        help="TLS certificate file path (may contain full chain). Default: cert.pem")
+    parser.add_argument("--key", default="key.pem",
+                        help="TLS private key file path. Default: key.pem")
+    parser.add_argument("--cert-chain", action="append", dest="cert_chain",
+                        help="Intermediate certificate file (can be used multiple times for long chains)")
+
+    # WebTransport server settings
+    parser.add_argument("--wt-host", default="0.0.0.0",
+                        help="WebTransport server host. Default: 0.0.0.0")
+    parser.add_argument("--wt-port", type=int, default=4433,
+                        help="WebTransport server port. Default: 4433")
+
+    # QUIC server settings
+    parser.add_argument("--quic-host", default="0.0.0.0",
+                        help="QUIC server host. Default: 0.0.0.0")
+    parser.add_argument("--quic-port", type=int, default=4433,
+                        help="QUIC server port. Default: 4433 (or 4443 in net mode)")
+
+    # Static HTTPS server settings
+    parser.add_argument("--static", dest="static", action="store_true", default=True,
+                        help="Enable static HTTPS server for client files (default in wt mode)")
+    parser.add_argument("--no-static", dest="static", action="store_false",
+                        help="Disable static HTTPS server")
+    parser.add_argument("--static-host", default=None,
+                        help="Static server host. Default: same as wt-host")
+    parser.add_argument("--static-port", type=int, default=8443,
+                        help="Static server port. Default: 8443")
+    parser.add_argument("--static-root", default="client",
+                        help="Static files directory. Default: client")
+
+    # Game configuration
+    parser.add_argument("--width", type=int, default=60,
+                        help="Field width (3-255). Default: 60")
+    parser.add_argument("--height", type=int, default=40,
+                        help="Field height (3-255). Default: 40")
+    parser.add_argument("--tick-rate", type=int, default=10,
+                        help="Server tick rate in TPS (5-30). Default: 10")
+    parser.add_argument("--wrap-edges", action="store_true", default=False,
+                        help="Enable edge wrapping (default: disabled)")
+    parser.add_argument("--apples-per-snake", type=int, default=1,
+                        help="Apples per connected snake (1-12). Default: 1")
+    parser.add_argument("--apples-cap", type=int, default=255,
+                        help="Maximum total apples (0-255). Default: 255")
+    parser.add_argument("--players-max", type=int, default=32,
+                        help="Maximum concurrent players. Default: 32")
+
+    # Logging and testing
+    parser.add_argument("--log-level", default="INFO",
+                        choices=["DEBUG", "INFO", "WARNING", "ERROR"],
+                        help="Logging level. Default: INFO")
+    parser.add_argument("--run-seconds", type=float, default=None,
+                        help="Optional timeout in seconds for testing")
+
+    args = parser.parse_args()
+
+    # Post-process: static-host defaults to wt-host
+    if args.static_host is None:
+        args.static_host = args.wt_host
+
+    # In net mode, default quic-port to 4443 if not explicitly set
+    if args.mode == "net" and "--quic-port" not in sys.argv:
+        args.quic_port = 4443
+
+    # Validate TLS files for modes that need them
+    if args.mode in ("wt", "quic", "net"):
+        import os
+        if not os.path.exists(args.cert):
+            parser.error(f"Certificate file not found: {args.cert}")
+        if not os.path.exists(args.key):
+            parser.error(f"Key file not found: {args.key}")
+
+    return args
 
 
 if __name__ == "__main__":
     try:
-        if any(a in ("-h", "--help") for a in sys.argv[1:]):
+        args = parse_args()
-            print(
+
-                "Usage: python run.py [--mode mem|quic|wt] [--log-level LEVEL] [--run-seconds N]\n"
-                "  TLS (for wt/quic): set QUIC_CERT/QUIC_KEY or WT_CERT/WT_KEY env vars\n"
-                "  WT static server (MODE=wt): STATIC=1 [STATIC_HOST/PORT/ROOT]\n"
-                "Examples:\n  MODE=wt QUIC_CERT=cert.pem QUIC_KEY=key.pem python run.py\n  MODE=mem python run.py"
-            )
-            sys.exit(0)
         # Logging setup
-        level = os.environ.get("LOG_LEVEL", "INFO").upper()
+        logging.basicConfig(
-        logging.basicConfig(level=getattr(logging, level, logging.INFO), format="[%(asctime)s] %(levelname)s: %(message)s")
+            level=getattr(logging, args.log_level.upper()),
-        mode = os.environ.get("MODE", "mem").lower()
+            format="[%(asctime)s] %(levelname)s: %(message)s"
-        if mode == "wt":
+        )
+
+        # Run appropriate mode
+        if args.mode == "wt":
             logging.info("Starting in WebTransport mode")
-            asyncio.run(run_webtransport())
+            asyncio.run(run_webtransport(args))
-        elif mode == "quic":
+        elif args.mode == "quic":
             logging.info("Starting in QUIC datagram mode")
-            asyncio.run(run_quic())
+            asyncio.run(run_quic(args))
-        else:
+        elif args.mode == "net":
+            logging.info("Starting in combined WebTransport+QUIC mode")
+            asyncio.run(run_net(args))
+        else:  # mem
             logging.info("Starting in in-memory transport mode")
-            asyncio.run(run_in_memory())
+            asyncio.run(run_in_memory(args))
     except KeyboardInterrupt:
         pass
-
-
-
-
-
-
-async def _run_tasks_with_optional_timeout(tasks):
-    """Await tasks, optionally honoring RUN_SECONDS env var to cancel after a timeout."""
-    timeout_s = os.environ.get("RUN_SECONDS")
-    if not timeout_s:
-        await asyncio.gather(*tasks)
-        return
-    try:
-        await asyncio.wait_for(asyncio.gather(*tasks), timeout=float(timeout_s))
-    except asyncio.TimeoutError:
-        logging.info("Timeout reached (RUN_SECONDS=%s); stopping server tasks...", timeout_s)
-        for t in tasks:
-            t.cancel()
-        await asyncio.gather(*tasks, return_exceptions=True)

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())

server/quic_transport.py

@@ -44,7 +44,7 @@ class GameQuicProtocol(QuicConnectionProtocol):  # type: ignore[misc]
     async def send_datagram(self, data: bytes) -> None:
         logging.debug("QUIC send datagram: %d bytes", len(data))
         self._quic.send_datagram_frame(data)  # type: ignore[attr-defined]
-        await self._loop.run_in_executor(None, self.transmit)  # type: ignore[attr-defined]
+        self.transmit()  # Send queued QUIC packets immediately
 
 
 class QuicWebTransportServer(DatagramServerTransport):
@@ -65,15 +65,20 @@ class QuicWebTransportServer(DatagramServerTransport):
             await proto.send_datagram(data)
 
     async def run(self) -> None:
-        configuration = QuicConfiguration(is_client=False, alpn_protocols=["h3"])
+        configuration = QuicConfiguration(
+            is_client=False,
+            alpn_protocols=["h3"],
+            max_datagram_frame_size=65536  # Enable QUIC datagrams
+        )
         configuration.load_cert_chain(self.certfile, self.keyfile)
 
-        async def _create_protocol(*args, **kwargs):
+        def _create_protocol(*args, **kwargs):
             return GameQuicProtocol(*args, on_datagram=self._on_datagram, peers=self._peers, **kwargs)
 
         logging.info("QUIC datagram server listening on %s:%d", self.host, self.port)
         self._server = await serve(self.host, self.port, configuration=configuration, create_protocol=_create_protocol)
         try:
-            await self._server.wait_closed()
+            # Wait indefinitely until cancelled (e.g., by KeyboardInterrupt or timeout)
+            await asyncio.Event().wait()
         finally:
             self._server.close()

server/server.py

@@ -1,4 +1,4 @@
-from __future__ import annotations
+from __future__ import annotations
 
 import asyncio
 from dataclasses import dataclass
@@ -136,7 +136,7 @@ class GameServer:
     # --- Simulation ---
 
     def _consume_input_for_snake(self, s: Snake) -> None:
-        # Consume at most one input; skip 180° turns when length>1
+        # Consume at most one input; skip 180° turns when length>1
         while s.input_buf:
             nd = s.input_buf[0]
             # 180-degree check
@@ -452,7 +452,7 @@ class GameServer:
             full = pack_header(
                 self.runtime.version, PacketType.STATE_FULL, 0, self.runtime.next_seq(), self.runtime.state.tick & 0xFFFF
             ) + body
-        await self.transport.send(full, peer)
+            await self.transport.send(full, peer)
         else:
             # Partition by packing whole snakes first, apples only in first part; chunk a single oversized snake using 2-bit chunks
             update_id = self.runtime.next_update_id()
@@ -507,7 +507,7 @@ class GameServer:
                         dir_capacity_bytes = max(0, budget - overhead)
                         if dir_capacity_bytes <= 0:
                             break
-                        # Convert capacity bytes to number of directions (each 2 bits → 4 dirs per byte)
+                        # Convert capacity bytes to number of directions (each 2 bits → 4 dirs per byte)
                         dir_capacity = dir_capacity_bytes * 4
                         if dir_capacity <= 0:
                             break
@@ -571,6 +571,33 @@ class GameServer:
         if player_id is None:
             return
         logging.debug("INPUT from player_id=%d: %d events (base_tick=%d)", player_id, len(events), base_tick)
+
+        # Apply inputs to snake buffer (client-side filtering already applied)
+        snake = self.runtime.state.snakes.get(player_id)
+        if snake is not None:
+            for ev in events:
+                # Apply input buffer rules from project plan:
+                # - Max capacity 3
+                # - If opposite to last buffered, replace last
+                # - Drop duplicates
+                # - Overflow: replace last
+                if len(snake.input_buf) > 0:
+                    last_dir = snake.input_buf[-1]
+                    # Check if opposite (XOR == 2)
+                    if (int(ev.direction) ^ int(last_dir)) == 2:
+                        # Replace last
+                        snake.input_buf[-1] = ev.direction
+                        continue
+                    # Check if duplicate
+                    if ev.direction == last_dir:
+                        continue
+                # Add to buffer
+                if len(snake.input_buf) < 3:
+                    snake.input_buf.append(ev.direction)
+                else:
+                    # Overflow: replace last
+                    snake.input_buf[-1] = ev.direction
+
         # Relay to others immediately for prediction
         await self.relay_input_broadcast(
             from_player_id=player_id,

server/static_server.py

@@ -3,25 +3,66 @@ from __future__ import annotations
 import ssl
 import logging
 import threading
+import json
 from http.server import ThreadingHTTPServer, SimpleHTTPRequestHandler
 from pathlib import Path
-from typing import Tuple
+from typing import Tuple, Optional
 
 
 class _Handler(SimpleHTTPRequestHandler):
-    # Allow passing a base directory at construction time
+    # Allow passing a base directory and cert_hash_json at construction time
+    cert_hash_json: Optional[str] = None
+
     def __init__(self, *args, directory: str | None = None, **kwargs):
         super().__init__(*args, directory=directory, **kwargs)
 
+    def end_headers(self):
+        # Add no-cache headers for all static files to force browser to fetch fresh versions
+        self.send_header('Cache-Control', 'no-cache, no-store, must-revalidate')
+        self.send_header('Pragma', 'no-cache')
+        self.send_header('Expires', '0')
+        super().end_headers()
 
-def start_https_static(host: str, port: int, certfile: str, keyfile: str, docroot: str) -> Tuple[ThreadingHTTPServer, threading.Thread]:
+    def do_GET(self):
+        # Intercept /cert-hash.json requests
+        if self.path == '/cert-hash.json' and self.cert_hash_json:
+            self.send_response(200)
+            self.send_header('Content-Type', 'application/json')
+            self.send_header('Access-Control-Allow-Origin', '*')
+            self.end_headers()
+            self.wfile.write(self.cert_hash_json.encode('utf-8'))
+        else:
+            # Serve regular static files
+            super().do_GET()
+
+
+def start_https_static(
+    host: str,
+    port: int,
+    certfile: str,
+    keyfile: str,
+    docroot: str,
+    cert_hash_json: Optional[str] = None
+) -> Tuple[ThreadingHTTPServer, threading.Thread]:
     """Start a simple HTTPS static file server in a background thread.
 
+    Args:
+        host: Host to bind to
+        port: Port to bind to
+        certfile: Path to TLS certificate
+        keyfile: Path to TLS private key
+        docroot: Document root directory
+        cert_hash_json: Optional JSON string to serve at /cert-hash.json
+
     Returns the (httpd, thread). Caller is responsible for calling httpd.shutdown()
     to stop the server on application exit.
     """
     docroot_path = str(Path(docroot).resolve())
 
+    # Set class variable for the handler
+    if cert_hash_json:
+        _Handler.cert_hash_json = cert_hash_json
+
     def handler(*args, **kwargs):
         return _Handler(*args, directory=docroot_path, **kwargs)
 

server/utils.py

@@ -1,5 +1,11 @@
 from __future__ import annotations
 
+import hashlib
+import re
+import tempfile
+from typing import List, Optional
+from pathlib import Path
+
 
 def is_newer(a: int, b: int) -> bool:
     """Return True if 16-bit sequence number a is newer than b (wrap-aware).
@@ -8,3 +14,129 @@ def is_newer(a: int, b: int) -> bool:
     """
     return ((a - b) & 0xFFFF) < 0x8000
 
+
+def get_cert_sha256_hash(cert_path: str) -> str:
+    """Calculate SHA-256 hash of a certificate file.
+
+    Returns the hash as a lowercase hex string (64 characters).
+    This hash can be used by WebTransport clients for certificate pinning.
+    """
+    try:
+        from cryptography import x509
+        from cryptography.hazmat.backends import default_backend
+
+        # Read the certificate file
+        with open(cert_path, 'rb') as f:
+            cert_data = f.read()
+
+        # Parse the certificate
+        cert = x509.load_pem_x509_certificate(cert_data, default_backend())
+
+        # Get the DER-encoded certificate and hash it
+        cert_der = cert.public_bytes(encoding=x509.Encoding.DER)
+        hash_bytes = hashlib.sha256(cert_der).digest()
+
+        # Return as hex string
+        return hash_bytes.hex()
+    except Exception as e:
+        # Fallback: just hash the file contents (less accurate but works)
+        with open(cert_path, 'rb') as f:
+            return hashlib.sha256(f.read()).digest().hex()
+
+
+def split_pem_certificates(pem_data: str) -> List[str]:
+    """Split a PEM file containing multiple certificates into individual certs.
+
+    Args:
+        pem_data: String containing one or more PEM certificates
+
+    Returns:
+        List of individual certificate strings (each includes BEGIN/END markers)
+    """
+    # Match all certificate blocks
+    cert_pattern = r'(-----BEGIN CERTIFICATE-----.*?-----END CERTIFICATE-----)'
+    certificates = re.findall(cert_pattern, pem_data, re.DOTALL)
+    return certificates
+
+
+def combine_cert_chain(cert_path: str, chain_paths: List[str]) -> str:
+    """Combine server cert and chain certs into a single properly-formatted PEM file.
+
+    Args:
+        cert_path: Path to server certificate (may contain full chain)
+        chain_paths: List of paths to intermediate/root certificates (optional)
+
+    Returns:
+        Path to temporary combined certificate file (caller should clean up)
+    """
+    combined_content = []
+
+    # Read server certificate file
+    with open(cert_path, 'r') as f:
+        cert_data = f.read().strip()
+        certs = split_pem_certificates(cert_data)
+
+        if chain_paths:
+            # If chain files provided separately, only use first cert from cert_path
+            if certs:
+                combined_content.append(certs[0].strip())
+            else:
+                combined_content.append(cert_data)
+        else:
+            # No separate chain files - include all certs from cert_path (fullchain case)
+            if certs:
+                combined_content.extend([c.strip() for c in certs])
+            else:
+                combined_content.append(cert_data)
+
+    # Read separate chain certificate files
+    for chain_path in chain_paths:
+        with open(chain_path, 'r') as f:
+            chain_data = f.read().strip()
+            # Each chain file might contain multiple certs
+            chain_certs = split_pem_certificates(chain_data)
+            if chain_certs:
+                combined_content.extend([c.strip() for c in chain_certs])
+            else:
+                combined_content.append(chain_data)
+
+    # Write to temporary file with proper formatting
+    # Each cert should be separated by a newline
+    temp_file = tempfile.NamedTemporaryFile(mode='w', suffix='.pem', delete=False)
+    temp_file.write('\n'.join(combined_content))
+    temp_file.write('\n')  # End with newline
+    temp_file.close()
+
+    return temp_file.name
+
+
+def extract_server_cert(cert_path: str) -> str:
+    """Extract just the server certificate from a file that may contain a full chain.
+
+    Args:
+        cert_path: Path to certificate file (may contain chain)
+
+    Returns:
+        Path to temporary file containing only the server certificate
+    """
+    with open(cert_path, 'r') as f:
+        cert_data = f.read()
+
+    # Split into individual certificates
+    certs = split_pem_certificates(cert_data)
+
+    if not certs:
+        # No certs found, return original path
+        return cert_path
+
+    # First cert is the server cert
+    server_cert = certs[0].strip()
+
+    # Write to temporary file
+    temp_file = tempfile.NamedTemporaryFile(mode='w', suffix='.pem', delete=False)
+    temp_file.write(server_cert)
+    temp_file.write('\n')
+    temp_file.close()
+
+    return temp_file.name
+

server/webtransport_server.py

@@ -2,7 +2,7 @@ from __future__ import annotations
 
 import asyncio
 from dataclasses import dataclass
-from typing import Awaitable, Callable, Dict, Optional
+from typing import Callable, Dict, Optional
 
 from .transport import DatagramServerTransport, OnDatagram, TransportPeer
 import logging
@@ -11,7 +11,8 @@ import logging
 try:
     from aioquic.asyncio import QuicConnectionProtocol, serve
     from aioquic.quic.configuration import QuicConfiguration
-    from aioquic.h3.connection import H3Connection
+    from aioquic.quic.events import ProtocolNegotiated
+    from aioquic.h3.connection import H3_ALPN, H3Connection
     from aioquic.h3.events import HeadersReceived
     # Datagram event names vary by aioquic version; try both
     try:
@@ -21,6 +22,8 @@ try:
 except Exception:  # pragma: no cover - optional dependency not installed
     QuicConnectionProtocol = object  # type: ignore
     QuicConfiguration = object  # type: ignore
+    ProtocolNegotiated = object  # type: ignore
+    H3_ALPN = []  # type: ignore
     H3Connection = object  # type: ignore
     HeadersReceived = object  # type: ignore
     H3DatagramReceived = object  # type: ignore
@@ -38,55 +41,75 @@ class GameWTProtocol(QuicConnectionProtocol):  # type: ignore[misc]
         super().__init__(*args, **kwargs)
         self._on_datagram = on_datagram
         self._sessions = sessions
-        self._http: Optional[H3Connection] = None
+        self._http: Optional[H3Connection] = None  # Created after ProtocolNegotiated
+        logging.debug("GameWTProtocol initialized")
 
     def http_event_received(self, event) -> None:  # type: ignore[override]
+        logging.debug("HTTP event received: %s", type(event).__name__)
         # Headers for CONNECT :protocol = webtransport open a session
         if isinstance(event, HeadersReceived):
             headers = {k.decode().lower(): v.decode() for k, v in event.headers}
+            logging.debug("HeadersReceived: %s", headers)
             method = headers.get(":method")
             protocol = headers.get(":protocol") or headers.get("sec-webtransport-protocol")
+            logging.debug("Method: %s, Protocol: %s", method, protocol)
             if method == "CONNECT" and (protocol == "webtransport"):
-                # In WebTransport over H3, datagrams use the CONNECT stream id as flow_id
+                # In WebTransport over H3, datagrams use the CONNECT stream id as session id
-                flow_id = event.stream_id  # type: ignore[attr-defined]
+                session_id = event.stream_id  # type: ignore[attr-defined]
-                self._sessions[flow_id] = WTSession(flow_id=flow_id, proto=self)
+                self._sessions[session_id] = WTSession(flow_id=session_id, proto=self)
-                logging.info("WT CONNECT accepted: flow_id=%s", flow_id)
+                logging.info("WT CONNECT accepted: session_id=%s", session_id)
                 # Send 2xx to accept the session
                 if self._http is not None:
                     self._http.send_headers(event.stream_id, [(b":status", b"200")])
+                    self.transmit()  # Actually send the response to complete handshake
+                    logging.debug("Sent 200 response for WT CONNECT")
+            else:
+                logging.warning("Unexpected CONNECT: method=%s, protocol=%s", method, protocol)
         elif isinstance(event, H3DatagramReceived):  # type: ignore[misc]
-            # Route datagram to session by flow_id
+            # Route datagram to session by stream_id (WebTransport session ID)
-            flow_id = getattr(event, "flow_id", None)
+            # DatagramReceived has: stream_id (session), data (payload)
+            session_id = getattr(event, "stream_id", None)
             data = getattr(event, "data", None)
-            if flow_id is None or data is None:
+            logging.debug("DatagramReceived event: session_id=%s, data_len=%s, has_data=%s",
+                         session_id, len(data) if data else None, data is not None)
+            if session_id is None or data is None:
+                logging.warning("Invalid datagram event: session_id=%s, data=%s", session_id, data)
                 return
-            sess = self._sessions.get(flow_id)
+            sess = self._sessions.get(session_id)
             if not sess:
+                logging.warning("No session found for datagram: session_id=%s", session_id)
                 return
-            peer = TransportPeer(addr=(self, flow_id))
+            peer = TransportPeer(addr=(self, session_id))
-            logging.debug("WT datagram received: flow_id=%s, %d bytes", flow_id, len(data))
+            logging.info("WT datagram received: session_id=%s, %d bytes", session_id, len(data))
             asyncio.ensure_future(self._on_datagram(bytes(data), peer))
 
     def quic_event_received(self, event) -> None:  # type: ignore[override]
-        # Lazily create H3 connection wrapper
+        event_name = type(event).__name__
-        if self._http is None and hasattr(self, "_quic"):
+        logging.debug("QUIC event received: %s", event_name)
-            try:
+
-                self._http = H3Connection(self._quic, enable_webtransport=True)  # type: ignore[attr-defined]
+        # Create H3Connection after ALPN protocol is negotiated
-            except Exception:
+        if isinstance(event, ProtocolNegotiated):
-                self._http = None
+            if event.alpn_protocol in H3_ALPN:
+                self._http = H3Connection(self._quic, enable_webtransport=True)
+                logging.info("H3Connection created with WebTransport support (ALPN: %s)", event.alpn_protocol)
+            else:
+                logging.warning("Unexpected ALPN protocol: %s", event.alpn_protocol)
+
+        # Pass event to HTTP layer if connection is established
         if self._http is not None:
             for http_event in self._http.handle_event(event):
                 self.http_event_received(http_event)
 
     async def send_h3_datagram(self, flow_id: int, data: bytes) -> None:
-        if self._http is None:
-            return
         try:
+            if self._http is None:
+                logging.warning("Cannot send datagram: H3Connection not established")
+                return
             logging.debug("WT send datagram: flow_id=%s, %d bytes", flow_id, len(data))
-            self._http.send_datagram(flow_id, data)
+            self._http.send_datagram(stream_id=flow_id, data=data)
-            await self._loop.run_in_executor(None, self.transmit)  # type: ignore[attr-defined]
+            self.transmit()  # Send queued QUIC packets immediately
-        except Exception:
+        except Exception as e:
-            pass
+            logging.debug("Failed to send datagram: %s", e)
 
 
 class WebTransportServer(DatagramServerTransport):
@@ -115,15 +138,34 @@ class WebTransportServer(DatagramServerTransport):
                 await proto.send_h3_datagram(flow_id, data)
 
     async def run(self) -> None:
-        configuration = QuicConfiguration(is_client=False, alpn_protocols=["h3"])
+        from aioquic.quic.logger import QuicFileLogger
-        configuration.load_cert_chain(self.certfile, self.keyfile)
+        import os
 
-        async def _create_protocol(*args, **kwargs):
+        # Enable QUIC logging if debug level
+        quic_logger = None
+        if logging.getLogger().getEffectiveLevel() <= logging.DEBUG:
+            log_dir = os.path.join(os.getcwd(), "quic_logs")
+            os.makedirs(log_dir, exist_ok=True)
+            quic_logger = QuicFileLogger(log_dir)
+            logging.info("QUIC logging enabled in: %s", log_dir)
+
+        configuration = QuicConfiguration(
+            is_client=False,
+            alpn_protocols=["h3"],  # HTTP/3 with WebTransport support
+            max_datagram_frame_size=65536,  # Enable QUIC datagrams (required for WebTransport)
+            quic_logger=quic_logger
+        )
+        configuration.load_cert_chain(self.certfile, self.keyfile)
+        logging.debug("QUIC configuration: ALPN=%s, max_datagram_frame_size=%d",
+                     configuration.alpn_protocols, configuration.max_datagram_frame_size or 0)
+
+        def _create_protocol(*args, **kwargs):
             return GameWTProtocol(*args, on_datagram=self._on_datagram, sessions=self._sessions, **kwargs)
 
         logging.info("WebTransport (H3) server listening on %s:%d", self.host, self.port)
         self._server = await serve(self.host, self.port, configuration=configuration, create_protocol=_create_protocol)
         try:
-            await self._server.wait_closed()
+            # Wait indefinitely until cancelled (e.g., by KeyboardInterrupt or timeout)
+            await asyncio.Event().wait()
         finally:
             self._server.close()

test_http3.py

@@ -0,0 +1,59 @@
+#!/usr/bin/env python3
+"""Simple HTTP/3 client to test the server."""
+
+import asyncio
+import logging
+from aioquic.asyncio import connect
+from aioquic.quic.configuration import QuicConfiguration
+
+logging.basicConfig(level=logging.DEBUG)
+
+async def test_http3(url: str):
+    """Test HTTP/3 connection to the server."""
+    print(f"Testing HTTP/3 connection to: {url}")
+
+    # Parse URL
+    if url.startswith("https://"):
+        url = url[8:]
+
+    host, port = url.split(":")
+    port = int(port.rstrip("/"))
+
+    print(f"Connecting to {host}:{port}...")
+
+    # Create QUIC configuration
+    configuration = QuicConfiguration(
+        is_client=True,
+        alpn_protocols=["h3"],
+        verify_mode=0  # Skip certificate verification for testing
+    )
+
+    try:
+        async with connect(
+            host,
+            port,
+            configuration=configuration,
+        ) as protocol:
+            print(f"✓ QUIC connection established!")
+            print(f"  ALPN protocol: {protocol._quic.tls.alpn_negotiated}")
+            print(f"  Remote address: {protocol._quic.remote_address}")
+
+            # Just test the connection, don't send HTTP requests yet
+            await asyncio.sleep(1)
+
+            print("✓ Connection successful!")
+            return True
+
+    except Exception as e:
+        print(f"✗ Connection failed: {e}")
+        import traceback
+        traceback.print_exc()
+        return False
+
+if __name__ == "__main__":
+    import sys
+
+    url = sys.argv[1] if len(sys.argv) > 1 else "https://127.0.0.1:4433"
+
+    success = asyncio.run(test_http3(url))
+    sys.exit(0 if success else 1)

test_webtransport_client.py

@@ -0,0 +1,188 @@
+#!/usr/bin/env python3
+"""
+WebTransport test client to verify server is working correctly.
+"""
+
+import asyncio
+import logging
+import sys
+from typing import Optional
+
+from aioquic.asyncio.client import connect
+from aioquic.asyncio.protocol import QuicConnectionProtocol
+from aioquic.h3.connection import H3Connection
+from aioquic.h3.events import DatagramReceived, H3Event, HeadersReceived
+from aioquic.quic.configuration import QuicConfiguration
+from aioquic.quic.events import QuicEvent
+
+logging.basicConfig(
+    level=logging.DEBUG,
+    format="[%(asctime)s] %(levelname)s: %(message)s"
+)
+
+logger = logging.getLogger(__name__)
+
+
+class WebTransportClient(QuicConnectionProtocol):
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self._http: Optional[H3Connection] = None
+        self._session_id: Optional[int] = None
+        self._session_established = asyncio.Event()
+        self._received_datagrams = []
+
+    def quic_event_received(self, event: QuicEvent) -> None:
+        logger.debug(f"QUIC event: {type(event).__name__}")
+
+        # Create H3Connection on first event
+        if self._http is None:
+            self._http = H3Connection(self._quic, enable_webtransport=True)
+            logger.info("H3Connection created with WebTransport support")
+
+        # Process event through HTTP/3 layer
+        if self._http is not None:
+            for http_event in self._http.handle_event(event):
+                self.http_event_received(http_event)
+
+    def http_event_received(self, event: H3Event) -> None:
+        logger.debug(f"HTTP event: {type(event).__name__}")
+
+        if isinstance(event, HeadersReceived):
+            headers = dict(event.headers)
+            status = headers.get(b":status", b"").decode()
+            logger.info(f"Received headers: status={status}")
+
+            if status == "200" and self._session_id is None:
+                self._session_id = event.stream_id
+                logger.info(f"WebTransport session established! session_id={self._session_id}")
+                self._session_established.set()
+            else:
+                logger.error(f"WebTransport session rejected: status={status}, headers={headers}")
+
+        elif isinstance(event, DatagramReceived):
+            logger.info(f"Received datagram: {len(event.data)} bytes, flow_id={event.flow_id}")
+            self._received_datagrams.append(event.data)
+
+    async def establish_session(self, path: str = "/") -> None:
+        """Send WebTransport CONNECT request."""
+        logger.info(f"Sending WebTransport CONNECT request for path: {path}")
+
+        # Allocate stream ID for CONNECT request
+        stream_id = self._quic.get_next_available_stream_id()
+
+        # Send CONNECT request with WebTransport protocol
+        headers = [
+            (b":method", b"CONNECT"),
+            (b":scheme", b"https"),
+            (b":authority", b"np.vaku.org.ua:4433"),
+            (b":path", path.encode()),
+            (b":protocol", b"webtransport"),
+        ]
+
+        self._http.send_headers(stream_id=stream_id, headers=headers, end_stream=False)
+        self.transmit()
+
+        logger.info(f"WebTransport CONNECT sent on stream {stream_id}")
+
+        # Wait for session to be established
+        try:
+            await asyncio.wait_for(self._session_established.wait(), timeout=5.0)
+            logger.info("✓ WebTransport session established successfully!")
+            return True
+        except asyncio.TimeoutError:
+            logger.error("✗ Timeout waiting for WebTransport session acceptance")
+            return False
+
+    async def send_datagram(self, data: bytes) -> None:
+        """Send a datagram over the WebTransport session."""
+        if self._session_id is None:
+            logger.error("Cannot send datagram: session not established")
+            return
+
+        logger.info(f"Sending datagram: {len(data)} bytes")
+        self._http.send_datagram(stream_id=self._session_id, data=data)
+        self.transmit()
+
+    async def wait_for_datagram(self, timeout: float = 2.0) -> Optional[bytes]:
+        """Wait for a datagram response."""
+        logger.info(f"Waiting for datagram response (timeout={timeout}s)...")
+        start = asyncio.get_event_loop().time()
+
+        while asyncio.get_event_loop().time() - start < timeout:
+            if self._received_datagrams:
+                return self._received_datagrams.pop(0)
+            await asyncio.sleep(0.1)
+
+        logger.warning("No datagram received within timeout")
+        return None
+
+
+async def test_webtransport(host: str, port: int, verify_mode: bool = False):
+    """Test WebTransport connection to the server."""
+    logger.info(f"Testing WebTransport connection to {host}:{port}")
+
+    # Configure QUIC
+    configuration = QuicConfiguration(
+        is_client=True,
+        alpn_protocols=["h3"],  # HTTP/3
+        max_datagram_frame_size=65536,  # Enable QUIC datagrams (required for WebTransport)
+        verify_mode=0 if not verify_mode else 2,  # Skip cert verification for self-signed
+    )
+
+    try:
+        async with connect(
+            host,
+            port,
+            configuration=configuration,
+            create_protocol=WebTransportClient,
+        ) as client:
+            logger.info("✓ QUIC connection established")
+            client = client  # type: WebTransportClient
+
+            # Establish WebTransport session
+            if not await client.establish_session("/"):
+                logger.error("✗ Failed to establish WebTransport session")
+                return False
+
+            # Send a test datagram (simple game JOIN packet)
+            # Format: version(1) | type(1) | flags(1) | seq(2) | name_len(1) | name
+            test_packet = bytes([
+                0x01,  # version
+                0x01,  # JOIN packet type
+                0x00,  # flags
+                0x00, 0x01,  # seq=1
+                0x04,  # name length
+                ord('T'), ord('E'), ord('S'), ord('T'),  # name="TEST"
+            ])
+
+            await client.send_datagram(test_packet)
+            logger.info("✓ Test JOIN packet sent")
+
+            # Wait for response
+            response = await client.wait_for_datagram(timeout=3.0)
+            if response:
+                logger.info(f"✓ Received response: {len(response)} bytes")
+                logger.info(f"   Response hex: {response.hex()}")
+                return True
+            else:
+                logger.warning("Server did not respond to JOIN packet (might be normal if not implemented)")
+                return True  # Connection worked even if no response
+
+    except Exception as e:
+        logger.error(f"✗ Connection failed: {e}")
+        import traceback
+        traceback.print_exc()
+        return False
+
+
+if __name__ == "__main__":
+    if len(sys.argv) < 2:
+        print("Usage: python test_webtransport_client.py <host> [port]")
+        print("Example: python test_webtransport_client.py np.vaku.org.ua 4433")
+        sys.exit(1)
+
+    host = sys.argv[1]
+    port = int(sys.argv[2]) if len(sys.argv) > 2 else 4433
+
+    success = asyncio.run(test_webtransport(host, port))
+    sys.exit(0 if success else 1)