개발환경 네트워크 문제 개선

Assets/Scripts/CONNECTION_TROUBLESHOOTING.md

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+# Connection Failure Troubleshooting Guide
+
+## Problem: "Failed to connect to server" error
+
+### Quick Fixes to Try
+
+1. **Add NetworkDebugger to scene**
+   - Add `NetworkDebugger` component to NetworkManager
+   - Check Console for detailed connection logs
+   - Look for:
+     - Connection approval status
+     - Transport binding errors
+     - Timeout messages
+
+2. **Add NetworkConnectionFixer to scene**
+   - Add `NetworkConnectionFixer` component to NetworkManager
+   - Right-click component → "Fix All Known Issues"
+   - This auto-fixes common transport timeout issues
+
+3. **Check Firewall (Most Likely Cause)**
+   Even with port forwarding, Windows Firewall may block connections:
+   
+   **Windows:**
+   - Windows Security → Firewall & network protection → Allow an app through firewall
+   - Add Unity Editor AND your built executable
+   - Allow on both Private and Public networks
+   - Add exception for port 7777 (or your port)
+   
+   **Command Line (Quick Fix):**
+   ```
+   netsh advfirewall firewall add rule name="Unity Network" dir=in action=allow protocol=TCP localport=7777
+   ```
+
+4. **Verify Transport Settings**
+   In Play mode, on NetworkManager → UnityTransport:
+   - ConnectionData.Address should be `0.0.0.0` for Host/Server
+   - ConnectionData.Port should be 7777 (or your forwarded port)
+   - ServerListenAddress can be left default
+
+5. **Test Port Forwarding**
+   - Use online tool: https://www.yougetsignal.com/tools/open-ports/
+   - Enter your public IP and port
+   - Should show "Open" (not "Closed" or "Timed out")
+
+6. **Disable IPv6 (Temporary Fix)**
+   Some network configurations have IPv6 issues:
+   ```
+   Control Panel → Network and Internet → Network Connections
+   → Right-click adapter → Properties → Uncheck Internet Protocol Version 6
+   ```
+   (Reboot required)
+
+7. **Increase Network Timeouts**
+   - On UnityTransport component:
+   - Connect Timeout MS: 15000 (15 seconds)
+   - Max Connect Attempts: 10
+
+## Debug Steps
+
+### 1. Check Server Side
+```
+Add NetworkDebugger → Play → Start Host
+Check Console for:
+  ✓ "Server Started Successfully"
+  ✓ "Listening on: 0.0.0.0:7777"
+  ✗ Any binding errors
+```
+
+### 2. Check Client Side
+```
+Add NetworkDebugger → Play → Connect to PUBLIC IP
+Check Console for:
+  ✓ "Connection Approval Request from Client"
+  ✓ "Approval Response: Approved: true"
+  ✗ "TRANSPORT FAILURE"
+  ✗ "Failed to connect to server"
+```
+
+### 3. Common Error Patterns
+
+**Error: "Failed to connect to server" + "TRANSPORT FAILURE"**
+- Cause: Firewall blocking
+- Fix: Allow Unity through firewall, check port forwarding
+
+**Error: Connection approval never happens**
+- Cause: NetworkManager configuration issue
+- Fix: Check NetworkConfig → Connection Approval = true
+
+**Error: Client shows "Connected" but no player spawns**
+- Cause: ConnectionApproval returning false or spawn point issues
+- Fix: Check NetworkConnectionHandler logs
+
+## Advanced Troubleshooting
+
+### Log Network State
+```csharp
+// Add this component and right-click → "Log Current Network State"
+public void CheckConnection()
+{
+    Debug.Log("IsServer: " + NetworkManager.Singleton.IsServer);
+    Debug.Log("IsClient: " + NetworkManager.Singleton.IsClient);
+    Debug.Log("IsConnectedClient: " + NetworkManager.Singleton.IsConnectedClient);
+}
+```
+
+### Test Local Connection First
+1. Host: Connect to 127.0.0.1 (should always work)
+2. If fails: Project setup issue, not network issue
+3. If works: Network/Firewall issue with public IP
+
+### Check NetworkManager Configuration
+Ensure:
+- Player Prefab assigned
+- Network Prefabs list populated
+- Connection Approval enabled
+- Scene Management enabled (if using scenes)
+- Transport is Unity Transport (UTP)
+
+## Alternative Solutions
+
+### Option 1: Use LAN instead of Internet
+If possible, use VPN or Hamachi:
+- Creates virtual LAN
+- Both players appear on same network
+- No port forwarding needed
+
+### Option 2: Use Relay Service
+Unity Relay bypasses NAT/Firewall:
+- Requires Unity Services account
+- Free tier available
+- More reliable for internet play
+
+### Option 3: Dedicated Server
+- Host on cloud server (AWS, Azure, etc.)
+- No port forwarding needed on client side
+- Better performance and reliability
+
+## Quick Checklist
+
+- [ ] Port forwarded correctly (verify with online tool)
+- [ ] Firewall allows Unity/Build executable
+- [ ] Using public IP (not 127.0.0.1 or 192.168.x.x)
+- [ ] Same Unity version and Netcode version on both sides
+- [ ] Same port on both client and server
+- [ ] NetworkManager has Player Prefab assigned
+- [ ] Host started BEFORE client tries to connect
+- [ ] No antivirus/security software blocking
+- [ ] Both using Release builds (not Debug)
+
+## When to Ask for Help
+
+If you've tried:
+1. All firewall fixes
+2. Verified port forwarding with online tool
+3. Tested local connection (127.0.0.1) works
+4. Checked NetworkManager configuration
+5. Added NetworkDebugger and NetworkConnectionFixer
+
+Then share:
+- Full Console logs from BOTH host and client
+- NetworkManager inspector screenshot
+- UnityTransport settings screenshot
+- Port forwarding confirmation (screenshot or online tool result)