examples/ping: Add a ping example

examples/ping/server/main.go

@@ -0,0 +1,77 @@
+package main
+
+import "os"
+import "io"
+import "fmt"
+import "log"
+import "errors"
+import "git.tebibyte.media/sashakoshka/hopp"
+import "git.tebibyte.media/sashakoshka/hopp/examples/ping"
+
+func main() {
+	name := os.Args[0]
+	if len(os.Args) != 2 {
+		fmt.Fprintf(os.Stderr, "Usage: %s HOST:PORT\n", name)
+		os.Exit(2)
+	}
+	address  := os.Args[1]
+	err := listen(address)
+	handleErr(1, err)
+}
+
+func listen(address string) error {
+	listener, err := hopp.Listen("tcp", address, nil)
+	if err != nil { return err }
+	log.Printf("(i) hosting on %s", address)
+	for {
+		conn, err := listener.Accept()
+		if err != nil { return err }
+		go run(conn)
+	}
+}
+
+func run(conn hopp.Conn) {
+	log.Printf("-=E %v connected", conn.RemoteAddr())
+	defer log.Printf("X=- %v disconnected", conn.RemoteAddr())
+	defer conn.Close()
+	
+	for {
+		trans, err := conn.AcceptTrans()
+		if err != nil {
+			if !errors.Is(err, io.EOF) {
+				log.Printf("XXX %v failed: %v", conn.RemoteAddr(), err)
+			}
+			return
+		}
+		go runTrans(conn, trans)
+	}
+}
+
+func runTrans(conn hopp.Conn, trans hopp.Trans) {
+	for {
+		message, _, err := ping.Receive(trans)
+		if err != nil {
+			if !errors.Is(err, io.EOF) {
+				log.Printf("XXX failed to receive message: %v", err)
+			}
+			return
+		}
+		switch message := message.(type) {
+		case *ping.MessagePing:
+			log.Printf("--> ping (%d) from %v", message, conn.RemoteAddr())
+			response := ping.MessagePong(*message)
+			_, err := ping.Send(trans, &response)
+			if err != nil {
+				log.Printf("XXX failed to send message: %v", err)
+				return
+			}
+		}
+	}
+}
+
+func handleErr(code int, err error) {
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "%s: %v\n", os.Args[0], err)
+		os.Exit(code)
+	}
+}