diff --git a/behaviortree_ros2/src/bt_executor_parameters.yaml b/behaviortree_ros2/src/bt_executor_parameters.yaml
index 7008953..5bc05ca 100644
--- a/behaviortree_ros2/src/bt_executor_parameters.yaml
+++ b/behaviortree_ros2/src/bt_executor_parameters.yaml
@@ -33,9 +33,9 @@ bt_server:
     type: int,
     default_value: 1667,
     read_only: true,
-    description: "Server port value to publish Groot2 messages on",
+    description: "Server port of the legacy debugger; its publisher uses groot2_port - 1",
     validation: {
-      bounds<>: [1, 49151]
+      bounds<>: [2, 49151]
     }
   }
   plugins: {
diff --git a/behaviortree_ros2/src/tree_execution_server.cpp b/behaviortree_ros2/src/tree_execution_server.cpp
index c5cdaa2..741d361 100644
--- a/behaviortree_ros2/src/tree_execution_server.cpp
+++ b/behaviortree_ros2/src/tree_execution_server.cpp
@@ -215,7 +215,11 @@ void TreeExecutionServer::execute(
     // Create shared_ptr to p_->tree without deleting capabilities
     auto non_deleting_tree_ptr = std::shared_ptr<BT::Tree>(&(p_->tree), [](BT::Tree*){ /* do nothing */ });
     BT::DebuggableTree debugTree{non_deleting_tree_ptr, true, debug_flag};
-    BT::PublisherZMQ publisher(debugTree, p_->params.groot2_port);
+    // The second argument of PublisherZMQ is the message rate, so the ports are passed explicitly: groot2_port is the
+    // server port and groot2_port - 1 the publisher port (1666 and 1667 by default). Two executors on one host need
+    // different values.
+    const auto groot2_port = static_cast<unsigned>(p_->params.groot2_port);
+    BT::PublisherZMQ publisher(debugTree, 25, groot2_port - 1, groot2_port);
 
     // Optional protocol-2 endpoint, independent of the existing Eurecat debugger.
     // Scope ensures destruction before the next goal replaces p_->tree.
@@ -223,8 +227,8 @@ void TreeExecutionServer::execute(
     if(p_->params.enable_bt_viewer)
     {
       const auto port = p_->params.bt_viewer_port;
-      // The legacy publisher above uses its default ports 1666 and 1667.
-      if(port <= 1667 && port + 1 >= 1666)
+      // The legacy publisher above uses groot2_port - 1 and groot2_port.
+      if(port <= p_->params.groot2_port && port + 1 >= p_->params.groot2_port - 1)
       {
         RCLCPP_WARN(kLogger, "BT viewer ports overlap legacy debugger; viewer disabled");
       }