NATS Configuration

OptionsRealTime uses NATS as its messaging server. Rover starts NATS automatically by default — most users never need to interact with NATS directly. This page documents the underlying nats.config file, useful when troubleshooting startup issues, customizing storage limits, or running against a centrally-managed NATS server in an institutional deployment.

File Location

<install dir>\nats.config

The installer generates this file with absolute paths on first install. Subsequent installs preserve the existing file.

Default Configuration

# NATS Server Configuration for OptionsRealTime
host: 0.0.0.0
port: 4222
http: 0.0.0.0:8222
max_payload: 67000000

websocket {
  host: 0.0.0.0
  port: 9222
  no_tls: true
}

jetstream {
  store_dir: "C:/Users/<username>/AppData/Local/OptionsRealTime/jetstream"
  max_memory_store: 1GB
  max_file_store: 50GB
  sync_interval: "2m"
}

Configuration Options

Network Settings

Setting	Default	Description
`host`	`0.0.0.0`	IP address to bind. `0.0.0.0` listens on all interfaces.
`port`	`4222`	Main NATS port for client connections
`http`	`0.0.0.0:8222`	HTTP monitoring endpoint
`max_payload`	`67000000`	Maximum message size in bytes (~64MB)

WebSocket Settings

Setting	Default	Description
`websocket.host`	`0.0.0.0`	IP address for WebSocket connections
`websocket.port`	`9222`	WebSocket port — used by browser clients
`websocket.no_tls`	`true`	TLS disabled for LAN use

JetStream Settings

Setting	Default	Description
`store_dir`	`<install>/jetstream`	Absolute path to JetStream data storage
`max_memory_store`	`1GB`	Maximum memory for stream storage
`max_file_store`	`50GB`	Maximum disk space for stream storage
`sync_interval`	`2m`	How often to sync data to disk

Common Scenarios

Single Machine (Default)

No changes needed. The default configuration works for single machine use, with Rover automatically managing the NATS lifecycle.

Multi-Machine Setup

See the Multi-Machine Setup guide for complete instructions, including firewall configuration.

Increase Storage Limits

jetstream {
  max_memory_store: 2GB
  max_file_store: 100GB
}

Important Notes

Absolute paths required — The store_dir must be an absolute path, not relative. The installer generates it as an absolute path automatically.
Forward slashes — Use forward slashes (/) in paths, not backslashes.
Config preserved on upgrade — The installer will not overwrite an existing nats.config. Your customizations are preserved.
Restart required — After editing nats.config, restart Rover. Rover picks up the new config when it spawns NATS on the next launch.

Troubleshooting

Problem	Solution
Remote machine can’t connect	See Multi-Machine Setup — includes firewall configuration
Browser shows no data	Verify the websocket block is present and port 9222 is open
JetStream data not persisting	Verify `store_dir` is an absolute path
Out of disk space errors	Increase `max_file_store` or clear old streams
Rover reports NATS won’t start	Check `<InstallDir>\logs\nats.log` for the underlying error. Common causes include another program using port 4222 or antivirus blocking `nats-server.exe`