Running

The nats-server has many command line options. To get started, you don’t have to specify anything. In the absence of any flags, the NATS server will start listening for NATS client connections on port 4222. By default, security is disabled.

Standalone

When the server starts it will print some information including where the server is listening for client connections:

  1. nats-server

Output

  1. [61052] 2021/10/28 16:53:38.003205 [INF] Starting nats-server
  2. [61052] 2021/10/28 16:53:38.003329 [INF]   Version:  2.6.1
  3. [61052] 2021/10/28 16:53:38.003333 [INF]   Git:      [not set]
  4. [61052] 2021/10/28 16:53:38.003339 [INF]   Name:     NDUP6JO4T5LRUEXZUHWXMJYMG4IZAJDNWETTA4GPJ7DKXLJUXBN3UP3M
  5. [61052] 2021/10/28 16:53:38.003342 [INF]   ID:       NDUP6JO4T5LRUEXZUHWXMJYMG4IZAJDNWETTA4GPJ7DKXLJUXBN3UP3M
  6. [61052] 2021/10/28 16:53:38.004046 [INF] Listening for client connections on 0.0.0.0:4222
  7. [61052] 2021/10/28 16:53:38.004683 [INF] Server is ready
  8. ...

Docker

If you are running your NATS server in a docker container:

  1. docker run -p 4222:4222 -ti nats:latest

Output

  1. [1] 2021/10/28 23:51:52.705376 [INF] Starting nats-server
  2. [1] 2021/10/28 23:51:52.705428 [INF]   Version:  2.6.1
  3. [1] 2021/10/28 23:51:52.705432 [INF]   Git:      [c91f0fe]
  4. [1] 2021/10/28 23:51:52.705439 [INF]   Name:     NB32AP7VSM3FTKTVEGPQ3OZWSE4T7PQDVJSJMGYFIDKJA6TQEZMV2JNN
  5. [1] 2021/10/28 23:51:52.705446 [INF]   ID:       NB32AP7VSM3FTKTVEGPQ3OZWSE4T7PQDVJSJMGYFIDKJA6TQEZMV2JNN
  6. [1] 2021/10/28 23:51:52.705448 [INF] Using configuration file: nats-server.conf
  7. [1] 2021/10/28 23:51:52.709505 [INF] Starting http monitor on 0.0.0.0:8222
  8. [1] 2021/10/28 23:51:52.709590 [INF] Listening for client connections on 0.0.0.0:4222
  9. [1] 2021/10/28 23:51:52.709882 [INF] Server is ready
  10. [1] 2021/10/28 23:51:52.710394 [INF] Cluster name is 3tlKqFWx91wnnAekR76U9V
  11. [1] 2021/10/28 23:51:52.710419 [WRN] Cluster name was dynamically generated, consider setting one
  12. [1] 2021/10/28 23:51:52.710446 [INF] Listening for route connections on 0.0.0.0:6222
  13. ...

JetStream

Remember that in order to enable JetStream and all the functionalities that use it you need to enable it on at least one of your servers

Command Line

Enable JetStream by specifying the -js flag when starting the NATS server.

$ nats-server -js

Configuration File

You can also enable JetStream through a configuration file. By default, the JetStream subsytem will store data in the /tmp directory. Here’s a minimal file that will store data in a local “nats” directory, suitable for development and local testing.

  1. nats-server -c js.conf
  1. # js.conf
  2. jetstream {
  3.    store_dir=nats
  4. }

Normally JetStream will be run in clustered mode and will replicate data, so the best place to store JetStream data would be locally on a fast SSD. One should specifically avoid NAS or NFS storage for JetStream. More information on containerized NATS is available here.