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148 lines
3.3 KiB
Markdown
148 lines
3.3 KiB
Markdown
## Protocol Demo
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The virtues of the NATS protocol manifest quickly when you experience how easy it is to use NATS. Because the NATS protocol is text-based, you can use NATS across virtually any platform or language. In the following demo we use [Telnet](https://en.wikipedia.org/wiki/Telnet).
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On the wire you can publish and subscribe using a simple [set of protocol commands](/documentation/internals/nats-protocol/).
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## Instructions
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**1. Open a terminal session.**
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You'll use this terminal as the subscriber.
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**2. Connect to NATS.**
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```
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telnet demo.nats.io 4222
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```
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Expected result:
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```
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$ telnet demo.nats.io 4222
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Trying 107.170.221.32...
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Connected to demo.nats.io.
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Escape character is '^]'.
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INFO {"server_id":"ad29ea9cbb16f2865c177bbd4db446ca","version":"0.6.8","go":"go1.5.1","host":"0.0.0.0","port":4222,"auth_required":false,"ssl_required":false,"max_payload":1048576}
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```
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**3. Run the subscriber.**
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Subscribe to the wildcard subject `foo.*` with subject ID of `90`.
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```
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sub foo.* 90
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```
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Subscriber result: `+OK` indicating successful interest registration.
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```
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sub foo.* 90
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+OK
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```
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**4. Open a second terminal window.**
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You'll use this terminal for the publisher.
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**5. Connect to NATS.**
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```
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telnet demo.nats.io 4222
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```
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Expected result:
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```
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$ telnet demo.nats.io 4222
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Trying 107.170.221.32...
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Connected to demo.nats.io.
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Escape character is '^]'.
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INFO {"server_id":"ad29ea9cbb16f2865c177bbd4db446ca","version":"0.6.8","go":"go1.5.1","host":"0.0.0.0","port":4222,"auth_required":false,"ssl_required":false,"max_payload":1048576}
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```
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**6. Publish a message.**
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The message includes the command (`pub`), subject (`foo.bar`), and length of the payload (`5`). Press enter and provide the payload (`hello`), then press enter again.
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```
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pub foo.bar 5
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hello
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```
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Publisher result: `+OK` indicating message publication.
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```
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pub foo.bar 5
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hello
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+OK
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```
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Subscriber result: `MSG` + subject name + subscription ID + message payload size + message payload `hello`.
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```
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sub foo.* 90
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+OK
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MSG foo.bar 90 5
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hello
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```
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**7. Publish another message with reply subject.**
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```
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pub foo.bar optional.reply.subject 5
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hello
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+OK
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```
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Subscriber result: `MSG` indicating message receipt.
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```
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MSG foo.bar 90 optional.reply.subject 5
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hello
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```
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**8. Unsubscribe from interest in the subject.**
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You can use the `UNSUB` command to unsubscribe from a message.
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Run the subscriber to unsubscribe:
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```
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unsub 90
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```
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Subscriber result: `+OK` indicating successful deregistration of interest.
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```
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unsub 90
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+OK
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```
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**9. Reconnect to server and subscribe.**
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```
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telnet demo.nats.io 4222
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```
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```
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sub foo.* 90
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```
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**10. Explore the ping/pong interval.**
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If you leave your telnet session open for a few minutes, you may notice that your clients receives `ping` requests from the server. If your client is not active, or does not respond to the server pings within the ping/pong interval, the server disconnects the client. The error message is `-ERR 'Stale Connection'`.
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You can send a `ping` request to the serve and receive a `PONG` reply. For example:
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```
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$ telnet demo.nats.io 4222
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Trying 107.170.221.32...
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Connected to demo.nats.io.
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Escape character is '^]'.
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INFO {"server_id":"ad29ea9cbb16f2865c177bbd4db446ca","version":"0.6.8","go":"go1.5.1","host":"0.0.0.0","port":4222,"auth_required":false,"ssl_required":false,"max_payload":1048576}
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ping
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PONG
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```
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