adding RPC server demo

Author: jkyberneees

src/main/java/samples/rpc/Server.java

@@ -0,0 +1,52 @@
+package samples.rpc;
+
+import realtime.pubsub.*;
+
+import java.util.Date;
+import java.util.Map;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+public class Server {
+
+    public static void main(String[] args) throws Exception {
+        var logger = Logger.getLogger(samples.ClientDemoMinimal.class.getName());
+
+        var accessToken = System.getenv("ACCESS_TOKEN");
+        var appId = System.getenv("APP_ID");
+
+        var config = new RealtimeClientConfig(() -> String.format("wss://genesis.r7.21no.de/apps/%s?access_token=%s", appId, accessToken));
+        var client = new RealtimeClient(config);
+
+        client.on("session.started", (Object... params) -> {
+            client.subscribeRemoteTopic("secure/inbound");
+        });
+
+        client.on("secure/inbound.presence", (Object... eventArgs) -> {
+            var messageEvent = (IncomingMessage) eventArgs[0];
+
+            var presenceMessage = PresenceMessage.from(messageEvent);
+            if (presenceMessage.getStatus() == PresenceStatus.CONNECTED) {
+                logger.info("Client " + presenceMessage.getConnectionId() + " connected...");
+            } else if (presenceMessage.getStatus() == PresenceStatus.DISCONNECTED) {
+                logger.info("Client " + presenceMessage.getConnectionId() + " disconnected...");
+            }
+        });
+
+        client.on("secure/inbound.gettime", (Object... eventArgs) -> {
+            var replyFn = (ReplyFunction) eventArgs[1];
+
+            logger.info("Responding to gettime request...");
+
+            // Send a reply
+            try {
+                var waitFor = replyFn.reply(Map.of("time", new Date()), "ok", false);
+                waitFor.waitForAck().thenAccept(ack -> logger.info("Acknowledgment received."));
+            } catch (Exception e) {
+                logger.log(Level.SEVERE, "Failed to send reply", e);
+            }
+        });
+
+        client.connect();
+    }
+}