Update main.cpp

main.cpp

@@ -310,7 +310,11 @@ private:
         if      (type == "operation")    handle_operation(msg, doc);
         else if (type == "cursor")       handle_cursor(msg);
         else if (type == "title_change") handle_title_change(msg);
-        else if (type == "ping")         { /* keep-alive, no-op */ }
+        else if (type == "ping") {
+            json pong = msg;
+            pong["type"] = "pong";
+            enqueue_send(pong.dump());
+        }
     }
 
     // ── Operation handler (with broadcast batching) ───────────────────────────
@@ -504,4 +508,4 @@ int main(int argc, char* argv[]) {
 
     ioc.run();
     return 0;
-}
+}