diff --git a/examples/ch4-01-rpc-inro/hello-service-v3/client/main.go b/examples/ch4-01-rpc-inro/hello-service-v3/client/main.go
new file mode 100644
index 0000000..a845ae5
--- /dev/null
+++ b/examples/ch4-01-rpc-inro/hello-service-v3/client/main.go
@@ -0,0 +1,36 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"log"
+	"net"
+	"net/rpc"
+	"net/rpc/jsonrpc"
+)
+
+var flagAddr = flag.String("addr", "localhost:1234", "server address")
+
+func main() {
+	flag.Parse()
+
+	// nc localhost 1234
+	// {"method":"HelloService.Hello","params":["hello"],"id":0}
+	// echo -e '{"method":"HelloService.Hello","params":["hello2222"],"id":3}' | nc localhost 1234
+	// echo -e '{"method":"HelloService.Hello","params":["hello2222"],"id":3}{"method":"HelloService.Hello","params":["hello33"],"id":4}' | nc localhost 1234
+
+	conn, err := net.Dial("tcp", *flagAddr)
+	if err != nil {
+		log.Fatal("net.Dial:", err)
+	}
+
+	client := rpc.NewClientWithCodec(jsonrpc.NewClientCodec(conn))
+
+	var reply string
+	err = client.Call("HelloService.Hello", "hello", &reply)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	fmt.Println(reply)
+}
diff --git a/examples/ch4-01-rpc-inro/hello-service-v3/server/main.go b/examples/ch4-01-rpc-inro/hello-service-v3/server/main.go
new file mode 100644
index 0000000..d93debc
--- /dev/null
+++ b/examples/ch4-01-rpc-inro/hello-service-v3/server/main.go
@@ -0,0 +1,40 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"log"
+	"net"
+	"net/rpc"
+	"net/rpc/jsonrpc"
+)
+
+type HelloService struct{}
+
+func (p *HelloService) Hello(request string, reply *string) error {
+	*reply = "hello:" + request
+	return nil
+}
+
+var flagPort = flag.Int("port", 1234, "listen port")
+
+func main() {
+	flag.Parse()
+
+	rpc.RegisterName("HelloService", new(HelloService))
+
+	// nc -l 2399
+	listener, err := net.Listen("tcp", fmt.Sprintf(":%d", *flagPort))
+	if err != nil {
+		log.Fatal("ListenTCP error:", err)
+	}
+
+	for {
+		conn, err := listener.Accept()
+		if err != nil {
+			log.Fatal("Accept error:", err)
+		}
+
+		go rpc.ServeCodec(jsonrpc.NewServerCodec(conn))
+	}
+}