private void removeSubscriptions(final Message<String> message) {
    final String connectionId = message.body();
    if (connectionId == null || "".equals(connectionId)) {
      LOG.warn("Received invalid connectionId ({}). No subscriptions removed.", connectionId);
    }

    LOG.debug("Removing subscription for connectionId {}", connectionId);

    subscriptions.values().stream()
        .filter(subscription -> subscription.getConnectionId().equals(connectionId))
        .forEach(subscription -> destroySubscription(subscription.getSubscriptionId()));
  }
The SubscriptionManager is responsible for managing subscriptions and sending messages to the
clients that have an active subscription.
ethereum/api/src/main/java/org/hyperledger/besu/ethereum/api/jsonrpc/websocket/subscription/SubscriptionManager.java