nwaku/docs/tutorial/jsonrpc-api.md

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# Waku v2 JSON-RPC API Basic Tutorial
## Background
This tutorial provides step-by-step instructions on how to start a `wakunode2` with the [JSON-RPC API](https://rfc.vac.dev/spec/16/) for basic peer-to-peer messaging using publish-subscribe (pubsub) patterns.
Libp2p pubsub-functionality is provided in Waku v2 and accessed via the [Relay API](https://rfc.vac.dev/spec/16/#relay-api).
Debugging methods are accessed via the [Debug API](https://rfc.vac.dev/spec/16/#debug-api).
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## Setup
Ensure you have built and run `wakunode2` as per [these instructions](https://github.com/status-im/nim-waku).
By default a running `wakunode2` will expose a JSON-RPC API on the localhost (`127.0.0.1`) at port `8545`.
It is possible to change this configuration by setting the `rpc-address` and `rpc-port` options when running the node:
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```
./build/wakunode2 --rpc-address:127.0.1.1 --rpc-port:8546
```
It is also possible to connect to one of our [testnets](https://github.com/status-im/nim-waku/blob/ee96705c7fbe4063b780ac43b7edee2f6c4e351b/docs/tutorial/dingpu.md) by specifying a `staticnode` when running the node:
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```
./build/wakunode2 --staticnode:<multiaddr>
```
where `<multiaddr>` is the multiaddress of a testnet node,
e.g. the dingpu cluster node at
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```
/ip4/134.209.139.210/tcp/60000/p2p/16Uiu2HAmJb2e28qLXxT5kZxVUUoJt72EMzNGXB47Rxx5hw3q4YjS
```
## Calling JSON-RPC methods
One way to access JSON-RPC methods is by using the `cURL` command line tool.
For example:
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```
curl -d '{"jsonrpc":"2.0","id":"id","method":"<method-name>", "params":[<params>]}' --header "Content-Type: application/json" http://localhost:8545
```
where `<method-name>` is the name of the JSON-RPC method to call and `<params>` is a comma-separated `Array` of parameters to pass as arguments to the selected method.
This assumes that the API is exposed on the `localhost` at port `8545` (the default configuration).
See [this page](https://rfc.vac.dev/spec/16/) for a full list of supported methods and parameters.
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## Perform a health check
You can perform a basic health check to verify that the `wakunode2` and API is up and running by calling the [`get_waku_v2_debug_v1_info` method](https://rfc.vac.dev/spec/16/#get_waku_v2_debug_v1_info) with no parameters.
A successful response contains the node's [`multiaddress`](https://docs.libp2p.io/concepts/addressing/).
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### Example request
```json
{
"jsonrpc": "2.0",
"id": "id",
"method": "get_waku_v2_debug_v1_info",
"params": []
}
```
### Example response
The response
```json
{
"jsonrpc": "2.0",
"id": "id",
"result": {
"listenAddresses": [
"/ip4/0.0.0.0/tcp/60000/p2p/16Uiu2HAmPv6Bq8kcmnM6gpLnjLwx3YuxN4B6AhWnN2bM9jutSS2Q"
]
}
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}
```
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indicates that the `wakunode2` is running and provides its multiaddress.
## Subscribe to a pubsub topic
You can subscribe to pubsub topics by calling the [`post_waku_v2_relay_v1_subscriptions` method](https://rfc.vac.dev/spec/16/#post_waku_v2_relay_v1_subscriptions) with an array of topic(s) as parameter.
Pubsub topics are in `String` format.
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### Example request
```json
{
"jsonrpc": "2.0",
"id": "id",
"method": "post_waku_v2_relay_v1_subscriptions",
"params": [
[
"my_topic_1",
"my_topic_2",
"my_topic_3"
]
]
}
```
### Example response
The response
```json
{
"jsonrpc": "2.0",
"id": "id",
"result": true,
"error": null
}
```
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indicates that the `wakunode2` successfully subscribed to all three requested topics.
## Publish to a pubsub topic
To publish a message to a pubsub topic, call the [`post_waku_v2_relay_v1_message` method](https://rfc.vac.dev/spec/16/#post_waku_v2_relay_v1_message) with the target topic and publishable message as parameters.
The message payload must be stringified as a hexadecimal string and wrapped in a [`WakuRelayMessage`](https://rfc.vac.dev/spec/16/#wakurelaymessage) `Object`.
Besides the published payload, a `WakuRelayMessage` can also contain an optional `contentTopic` that falls outside the scope of this tutorial.
See the [`WakuFilter` specification](https://rfc.vac.dev/spec/12/) for more information.
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### Example request
```json
{
"jsonrpc": "2.0",
"id": "id",
"method": "post_waku_v2_relay_v1_message",
"params": [
"my_topic_1",
{
"payload": "0x1a2b3c4d5e6f",
"timestamp": 1626813243.916377
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}
]
}
```
### Example response
The response
```json
{
"jsonrpc": "2.0",
"id": "id",
"result": true,
"error": null
}
```
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indicates that the message payload was successfully published to `"my_topic_1"`.
## Read new messages from a subscribed pubsub topic
Use the [`get_waku_v2_relay_v1_messages` method](https://rfc.vac.dev/spec/16/#get_waku_v2_relay_v1_messages) to retrieve the messages received on a subscribed pubsub topic.
The queried topic is passed as parameter.
This will only return new messages received after the last time this method was called.
Repeated calls to `get_waku_v2_relay_v1_messages` can therefore be used to continuously poll a topic for new messages.
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### Example request
```json
{
"jsonrpc": "2.0",
"id": "id",
"method": "get_waku_v2_relay_v1_messages",
"params": [
"my_topic_1"
]
}
```
### Example response
The response is an `Array` of [`WakuMessage` objects](https://rfc.vac.dev/spec/16/#wakumessage).
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```json
{
"jsonrpc": "2.0",
"id": "id",
"result": [
{
"payload": "0xaabbccddeeff",
"contentTopic": 0,
"version": 0
},
{
"payload": "0x112233445566",
"contentTopic": 0,
"version": 0
}
],
"error": null
}
```
Calling the same method again returns
```json
{
"jsonrpc": "2.0",
"id": "id",
"result": [],
"error": null
}
```
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indicating that no new messages were received on the subscribed topic.
## Unsubscribe from a pubsub topic
To unsubscribe from pubsub topics, call the [`delete_waku_v2_relay_v1_subscriptions` method](https://rfc.vac.dev/spec/16/#delete_waku_v2_relay_v1_subscriptions) with an array of topic(s) as parameter.
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### Example request
```json
{
"jsonrpc": "2.0",
"id": "id",
"method": "delete_waku_v2_relay_v1_subscriptions",
"params": [
[
"my_topic_1",
"my_topic_2"
]
]
}
```
### Example response
The response
```json
{
"jsonrpc": "2.0",
"id": "id",
"result": true,
"error": null
}
```
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indicates that the `wakunode2` successfully unsubscribed from both topics.