> For the complete documentation index, see [llms.txt](https://dev.teaproject.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://dev.teaproject.org/z_glossary/blockchain_listener.md).

# Blockchain Listener

All [state machine replicas](https://github.com/tearust/t-rust/blob/master/docs/_gitbook-dev-docs/z_glossary/state_machine_replica.md) nodes run a layer-1 client (either a full client or a light client). This layer-1 client will notify layer-2 when layer-1 events are triggered. The layer-2 runs a monitoring process that filters all events, only picking the events that are in the "waiting list" and then calling the layer-2 [state machine actor API](/z_glossary/state_machine_actor.md).

In the future, when the TEA Project is running above multiple layer-1 main chains, there would be multiple blockchain listeners for each main chain.