# WHATPORT(9009)

## NAME

port 9009 — ClickHouse interserver replication — ClickHouse's server-to-server port: replicas fetch data parts from each other here.

Protocol: TCP  
IANA: pichat

## DESCRIPTION

ClickHouse uses 9009 for inter-server communication — replication and data exchange between replicas at the low-level data access layer — separate from the 9000 native client protocol and the 8123 HTTP interface. On a ClickHouse cluster every node has it open to its peers. IANA registers 9009 as pichat, which you will not meet in practice.

## EXPOSURE

**Do not expose.** This is an internal cluster path that moves raw data parts between replicas; keep it on the cluster network and never route it from the internet.

## CHECK

```sh
sudo lsof -nP -iTCP:9009 -sTCP:LISTEN
```

## SEE ALSO

- docs — [ClickHouse — network ports (9009 inter-server communication)](https://clickhouse.com/docs/guides/sre/network-ports) (clickhouse.com)
- source — [ClickHouse/ClickHouse on GitHub](https://github.com/ClickHouse/ClickHouse) (github.com)
- iana — [IANA Service Name and Transport Protocol Port Number Registry — 9009](https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml?search=9009) (iana.org)

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HTML: <https://whatport.net/9009/> · JSON: <https://whatport.net/9009.json> · full dataset: <https://whatport.net/ports.json>