Flash multiplayer virtual worlds (Club Penguin, Habbo Hotel) were built on Flash's `XMLSocket` class, which communicated over persistent raw TCP sockets using null-byte (`\0`) terminated XML packets. Modern web games achieve lower latency and binary payload compression by migrating to standard **WebSockets** and Protocol Buffers.
1. Protocol Evolution: XMLSocket vs WebSocket + Protobuf
| Dimension | Flash XMLSocket (Legacy) | Modern WebSockets + Binary Protobuf |
|---|---|---|
| Transport Layer | Raw TCP Socket (Port 843 Policy File required) | HTTP/1.1 or HTTP/2 Upgrade to RFC 6455 WebSocket |
| Framing & Delimiter | Null Byte Character (\x00) delimiter | Native RFC 6455 2–10 byte frame headers with masking |
| Data Serialization | Verbose XML Text Strings (High bandwidth) | Compact Binary Protocol Buffers (Up to 85% smaller) |
| Encryption | Optional SSLSocket via TLS wrapper | Standard Secure WebSockets (wss://) over Port 443 |
