# Ping-Pong Example
This example demonstrates routing, serialization, and middleware usage in a
small ping/pong protocol. The server accepts a `Ping` message containing a
counter and responds with a `Pong` containing the incremented value. Logging
middleware prints each request and response.
```mermaid
classDiagram
class Ping {
+u32 0
+to_bytes()
+from_bytes()
}
class Pong {
+u32 0
+to_bytes()
+from_bytes()
}
class ErrorMsg {
+String 0
+to_bytes()
+from_bytes()
}
class PongMiddleware {
}
class PongService {
+inner: S
+call(req: ServiceRequest) Result<ServiceResponse, Infallible>
}
class Logging {
}
class LoggingService {
+inner: S
+call(req: ServiceRequest) Result<ServiceResponse, Infallible>
}
class HandlerService {
+id()
+from_service(id, service)
}
PongMiddleware --|> Transform
PongService --|> Service
Logging --|> Transform
LoggingService --|> Service
HandlerService <.. PongService : inner
HandlerService <.. LoggingService : inner
PongMiddleware ..> HandlerService : transform
Logging ..> HandlerService : transform
WireframeApp <.. build_app : factory
WireframeServer <.. main : uses
build_app --> WireframeApp
main --> WireframeServer
```