nips/200.md

NIP-200
=======

Nostr relay communication over HTTP(s) (NoH)
--------------------------------------------

`draft` `optional` `author:yonle`

This NIP describes the basic of communicating to relays over HTTP(S) requests.

## Communication between clients and relays

Relays may expose NoH endpoints that client could reach. Client may make HTTP requests to each relays endpoint for specified tasks as specified in NIP-11. Relays MAY limit number of requests from specific IP/Client/etc.

Relays must ensure that the NoH endpoints **MUST** be served with `Access-Control-Allow-Origin: *` header to ensure it can be validated by pure JS apps running in modern browsers.

### From client to relay: getting events and sending event

Client could make a request to `req` or `publish` endpoint that were specified in `/.well-known/nostr.json`

When fetching events, Client can optionally specify filters directly into the URI search query:
- `<req>?<filter>`

`<filter>` is a querystrings that determines what events will be received in that request. it can have the following attributes:

```
ids=<a list of event ids separated by commas>&
authors=<a list of lowercase pubkeys separated by commas>&
kinds=<a list of kinds numbers separated by commas>&
%23<single-letter (a-zA-Z)>=<a list of tag values separated by commas. for %23e — a list of event ids, for %23p — a list of event pubkeys>&
since=<an integer unix timestamp in seconds, events must be newer than this to pass>&
until=<an integer unix timestamp in seconds, events must be older than this to pass>&
limit=<maximum number of events relays SHOULD return in the initial query>
```

Request URL Examples:
- `https://my-relay.com/__nostr/req?kinds=0,1&limit=10`
- `https://my-relay.com/__nostr/req?authors=12345,67890`

To send event to relay, Client will need to make POST request to `publish` endpoint with POST body containing the JSON blob of the event.

### From relay to client: sending responses and notices

Every NoH response is a JSON body that contain the following JSON field:

- `results`: Array of relay response. Usually contain events requested by client.
- `notice`: Human readable error.

Relay may also respond with HTTP status code:

- `200`: OK / Success
- `400`: Invalid Request
- `500`: Relay/Server error