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

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Command Syntax

nats-server [server-options]

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Server Options Reference

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-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
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-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
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-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
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-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
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-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
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-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
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-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
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-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.
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-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, reloadSee Signals for detailed usage.
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--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
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--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.

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Complete Examples

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Basic Server

nats-server -p 4222 -m 8222

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Production Server

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

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Development Server with Custom Name

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

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Server Behind NAT

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

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Testing Configuration

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

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

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