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Wording/formatting changes, adding links, match up text and example

Signed-off-by: Matthias Hanel <mh@synadia.com>
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Matthias Hanel 2020-02-03 22:17:19 -05:00
parent 0de28c17df
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# Explore NATS Pub/Sub
NATS is a publish subscribe messaging system. Subscribers listening on a subject receive messages on that subject. If the subscriber is not actively listening on the subject, the message is not received. Subscribers can use the wildcard tokens such as `*` and `>` to match a single token or to match the tail of a subject.
NATS is a [publish subscribe](../../nats-concepts/pubsub.md) messaging system [based on subjects](../../nats-concepts/subjects.md). Subscribers listening on a subject receive messages published on that subject. If the subscriber is not actively listening on the subject, the message is not received. Subscribers can use the wildcard tokens such as `*` and `>` to match a single token or to match the tail of a subject.
![](../../.gitbook/assets/pubsubtut.svg)
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### 8. Verify message publication and receipt
You should see that the publisher sends the message: _Published \[msg.test\] : 'NATS MESSAGE'_
You should see that the publisher sends the message and prints: _Published \[msg.test\] : 'NATS MESSAGE'_
And that the subscriber receives the message: _\[\#1\] Received on \[msg.test\]: 'NATS MESSAGE'_
And that the subscriber receives the message and prints: _\[\#1\] Received on \[msg.test\]: 'NATS MESSAGE'_
Note that if the receiver does not get the message, check that you are using the same subject name for the publisher and the subscriber.
@ -94,7 +94,7 @@ Note that if the receiver does not get the message, check that you are using the
% go run nats-pub/main.go msg.test "NATS MESSAGE 2"
```
You should see that the subscriber receive message 2. Note that the message count is incremented each time your subscribing client receives a message on that subject:
You should see that the subscriber receives message 2. Note that the message count is incremented each time your subscribing client receives a message on that subject:
### 10. Start another shell or command prompt session
@ -106,7 +106,7 @@ You will use this session to run a second NATS subscriber.
% cd $GOPATH/src/github.com/nats-io/nats.go/examples
```
### 12. Subscribe to the message
### 12. Start a second client subscriber program
```bash
% go run nats-sub/main.go msg.test
@ -130,7 +130,7 @@ You will use this session to run a third NATS subscriber.
% cd $GOPATH/src/github.com/nats-io/nats.go/examples
```
### 16. Subscribe to a different message
### 16. Subscribe to a different subject
```bash
% go run nats-sub/main.go msg.test.new
@ -140,7 +140,7 @@ All the but last subscriber receives the message. Why? Because that subscriber i
### 17. Update the last subscriber to use a wildcard
NATS supports the use of wildcard characters for message subscribers. You cannot publish a message using a wildcard subject.
NATS supports the use of wildcard characters for message subscribers only. You cannot publish a message using a wildcard subject.
Change the last subscriber the listen on msg.\* and run it:

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# Explore NATS Queueing
NATS supports a form of load balancing using queue groups. Subscribers register a queue group name. A single subscriber in the group is randomly selected to receive the message.
NATS supports a form of load balancing using [queue groups](../../nats-concepts/queue.md). Subscribers register a queue group name. A single subscriber in the group is randomly selected to receive the message.
## Prerequisites
Go and the NATS server should be installed.
Go, node.js, ruby and the NATS server should be installed.
### 1. Start the NATS server
@ -20,7 +20,7 @@ git clone https://github.com/nats-io/nats.js.git
git clone https://github.com/nats-io/nats.rb.git
```
### 3. Run the Go client subscriber with queue group name
### 3. Run the Go client subscriber, providing a queue group name
```bash
cd $GOPATH/src/github.com/nats-io/nats.go/examples
@ -58,9 +58,9 @@ go run nats-pub/main.go foo "Hello NATS!"
### 8. Verify message publication and receipt
You should see that the publisher sends the message: _Published \[foo\] : 'Hello NATS!'_
You should see that the publisher the message and prints: _Published \[foo\] : 'Hello NATS!'_
You should see that only one of the my-queue group subscribers receives the message. In addition, the Go client subscriber not in the my-queue group should also receive the message.
You should see that only one of the my-queue group subscribers receives the message and prints it. In addition, the Go client subscriber not in the my-queue group should also receive and print the message.
### 9. Publish another message

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# Explore NATS Request/Reply
NATS supports request/reply messaging. In this tutorial you explore how to exchange point-to-point messages using NATS.
NATS supports [request/reply](../../nats-concepts/reqreply.md) messaging. In this tutorial you explore how to exchange point-to-point messages using NATS.
## Prerequisites
@ -25,18 +25,19 @@ You will use these sessions to run the NATS request and reply clients.
### 4. In one terminal, run the reply client listener
```bash
% go run nats-rply/main.go foo "this is my response"
% go run nats-rply/main.go help.please "OK, I CAN HELP!!!"
```
You should see the message `Receiver is listening`, and that the NATS receiver client is listening on the "help.please" subject. The reply client acts as a receiver, listening for message requests. In NATS, the receiver is a subscriber.
You should see the message: _Listening on \[help.please\]_
This means that the NATS receiver client is listening for requests messages on the "help.please" subject. In NATS, the receiver is a subscriber.
### 5. In the other terminal, run the request client
```bash
% go run nats-req/main.go foo "request payload"
% go run nats-req/main.go help.please "some message"
```
The NATS requestor client makes a request by sending the message "some message" on the “help.please” subject.
The NATS receiver client receives the message, formulates the reply \("OK, I CAN HELP!!!"\), and sends it to the inbox of the requester.