Server Options

Complete reference of NATS server command-line flags

Server options control the core behavior of the NATS server including network binding, monitoring, and server identification.

Command Syntax

nats-server [server-options]

Server Options Reference

-a, --addr, --net · string · default: "0.0.0.0"

Bind to host address. Specifies the network interface the server listens on for client connections.

Examples:

# Listen on all interfaces (default)
nats-server -a 0.0.0.0

# Listen on localhost only
nats-server -a 127.0.0.1

# Listen on specific interface
nats-server -a 192.168.1.10

-p, --port · number · default: "4222"

Use port for client connections. The default NATS client port is 4222.

Examples:

# Use default port
nats-server

# Use custom port
nats-server -p 4223

# Random available port
nats-server -p -1

-n, --name, --server_name · string · default: "auto"

Server name for identification. If not specified, a unique name is automatically generated.

Examples:

# Auto-generated name
nats-server

# Custom server name
nats-server -n nats-prod-01
nats-server --server_name nats-east-1

-P, --pid · string

File to store the server’s process ID. Useful for process management and sending signals.

Examples:

nats-server -P /var/run/nats-server.pid
nats-server --pid /tmp/nats.pid

-m, --http_port · number

Use port for HTTP monitoring endpoint. Enables the monitoring interface at http://<host>:<port>/varz, /connz, /subsz, etc.

Examples:

# Enable monitoring on default monitoring port
nats-server -m 8222

# Custom monitoring port
nats-server -m 9090

Access monitoring endpoints:

• http://localhost:8222/varz - General server information
• http://localhost:8222/connz - Connection information
• http://localhost:8222/subsz - Subscription information

-ms, --https_port · number

Use port for HTTPS monitoring. Same as -m but serves monitoring endpoints over HTTPS.

Examples:

nats-server -ms 8223 --tlscert server-cert.pem --tlskey server-key.pem

-c, --config · string

Configuration file path. The configuration file uses a flexible format for complex setups.

Examples:

# Load configuration file
nats-server -c /etc/nats/nats-server.conf
nats-server --config ./nats.conf

# Configuration with overrides
nats-server -c nats.conf -p 4223 -D

-t · boolean

Test configuration and exit. Validates the configuration file without starting the server.

Examples:

# Validate configuration
nats-server -c nats.conf -t

The server will print whether the configuration is valid and exit with status 0 on success.

-sl, --signal · string

Send signal to nats-server process. Used for process management without direct PID access.

Format: --signal <signal>[=<pid>]

Signals: ldm, stop, quit, term, reopen, reload

See Signals for detailed usage.

--client_advertise · string

Client URL to advertise to other servers. Useful when the server is behind NAT or in containerized environments.

Examples:

# Advertise public IP
nats-server --client_advertise nats://public.example.com:4222

# Advertise with custom port
nats-server -p 4222 --client_advertise nats://10.0.1.5:4222

--ports_file_dir · string

Creates a ports file in the specified directory. The file is named <executable_name>_<pid>.ports and contains the actual ports the server is listening on.

Examples:

nats-server --ports_file_dir /var/run/nats

This creates a file like /var/run/nats/nats-server_12345.ports containing:

nats-server: 4222
http: 8222

Useful when using -1 for random port assignment.

Complete Examples

Basic Server

nats-server -p 4222 -m 8222

Production Server

nats-server \
  -c /etc/nats/nats-server.conf \
  -P /var/run/nats-server.pid \
  -m 8222 \
  -l /var/log/nats-server.log

Development Server with Custom Name

nats-server -n dev-server -p 4223 -m 8223 -D

Server Behind NAT

nats-server \
  -a 0.0.0.0 \
  -p 4222 \
  --client_advertise nats://public-ip.example.com:4222

Testing Configuration

# Validate configuration
nats-server -c production.conf -t

# If valid, start the server
nats-server -c production.conf

Related Options

• Logging Options - Configure logging and debugging
• Signals - Send signals to running server