> ## Documentation Index > Fetch the complete documentation index at: https://docs.snek.fun/llms.txt > Use this file to discover all available pages before exploring further. # Charts WebSocket > Protocol v2 — LastBar and MCapBar streams Real-time **price bars** and **market-cap bars** use the same **WebSocket Protocol v2** as other Snekfun services: JSON text frames, subscribe / unsubscribe envelopes, and `DefaultOutgoingMessage` responses. **Auth:** Public ## Connection * **Public URL (typical):** `wss://charts.snek.fun/v1/websocket/ws` (reverse proxy adds `/websocket` before `/ws`). * **Application route:** the server binds WebSocket at path `/ws` on the charts WS port. Open the socket, then send **Connect** (optional depending on client) and **Subscribe** messages as JSON. ## Topics | Topic | Purpose | | --------- | ------------------------------------------------ | | `LastBar` | OHLCV updates for a `pair` + `interval` | | `MCapBar` | Market-cap bar updates for a `pair` + `interval` | ## Subscribe (client → server) ```json theme={null} { "messageType": "subscribe", "clientId": "my-client-1", "requestId": "req-001", "topic": "LastBar", "data": { "pair": { "base": "279c909f348e533da5808898f87f9a14bb2c3dfbbacccd631d927a3f.534e454b", "quote": "." }, "interval": "min1" } } ``` * `pair.base` / `pair.quote`: Cardano asset ids; ADA may be `"."`, `"ADA"`, or `"0x"` on input. * `interval`: `min1` | `min5` | `hour1` | `day1` | `week1` | `month1`. For **MCapBar**, set `"topic": "MCapBar"` with the same `data` shape. ## Unsubscribe ```json theme={null} { "messageType": "unsubscribe", "clientId": "my-client-1", "requestId": "req-001" } ``` ## Server → client Envelope: ```json theme={null} { "requestId": "req-001", "event": "LastBarUpdate", "messageType": "Response", "data": { "pair": "baseAsset_quoteAsset", "time": 1729459260, "low": "0.0998", "high": "0.1015", "open": "0.1001", "close": "0.1009", "volume": "345.67", "isRelevant": true } } ``` `MCapBarUpdate` events carry `mCap` instead of OHLCV fields. ## HTTP fallback Use [Charts HTTP](/api-reference/charts-ws/http) for historical ranges and initial snapshots if WebSocket is unavailable. ## AsyncAPI ````yaml api-reference/asyncapi.json charts id: charts title: Charts (Protocol v2) description: Topics LastBar and MCapBar with pair + interval in data. servers: - id: charts protocol: wss host: charts.snek.fun bindings: [] variables: [] address: /v1/websocket/ws parameters: [] bindings: [] operations: - &ref_3 id: sendCharts title: Send charts type: send messages: - &ref_5 id: Subscribe payload: - name: Subscribe description: Charts subscribe type: object properties: - name: messageType type: string description: subscribe required: true - name: clientId type: string required: true - name: requestId type: string required: true - name: topic type: string enumValues: - LastBar - MCapBar required: true - name: data type: object required: true properties: - name: pair type: object required: true properties: - name: base type: string required: true - name: quote type: string required: true - name: interval type: string enumValues: - min1 - min5 - hour1 - day1 - week1 - month1 required: true headers: [] jsonPayloadSchema: type: object required: - messageType - clientId - requestId - topic - data properties: messageType: type: string const: subscribe x-parser-schema-id: clientId: type: string x-parser-schema-id: requestId: type: string x-parser-schema-id: topic: type: string enum: - LastBar - MCapBar x-parser-schema-id: data: type: object required: - pair - interval properties: pair: type: object required: - base - quote properties: base: type: string x-parser-schema-id: quote: type: string x-parser-schema-id: x-parser-schema-id: interval: type: string enum: - min1 - min5 - hour1 - day1 - week1 - month1 x-parser-schema-id: x-parser-schema-id: x-parser-schema-id: SubscribeChartsPayloadV2 title: Subscribe description: Charts subscribe example: |- { "messageType": "subscribe", "clientId": "c1", "requestId": "r1", "topic": "LastBar", "data": { "pair": { "base": "policy.hex", "quote": "." }, "interval": "min1" } } bindings: [] extensions: - id: x-parser-unique-object-id value: Subscribe - &ref_6 id: Unsubscribe payload: - name: Unsubscribe type: object properties: - name: messageType type: string description: unsubscribe required: true - name: clientId type: string required: true - name: requestId type: string required: true headers: [] jsonPayloadSchema: type: object required: - messageType - clientId - requestId properties: messageType: type: string const: unsubscribe x-parser-schema-id: clientId: type: string x-parser-schema-id: requestId: type: string x-parser-schema-id: x-parser-schema-id: UnsubscribePayloadV2 title: Unsubscribe example: |- { "messageType": "unsubscribe", "clientId": "c1", "requestId": "r1" } bindings: [] extensions: - id: x-parser-unique-object-id value: Unsubscribe bindings: [] extensions: &ref_1 - id: x-parser-unique-object-id value: charts - &ref_2 id: receiveCharts title: Receive charts type: receive messages: - &ref_4 id: Outgoing payload: - name: Charts bar update type: object properties: - name: requestId type: &ref_0 - string - 'null' required: false - name: event type: string enumValues: - LastBarUpdate - MCapBarUpdate required: false - name: messageType type: string required: false - name: data type: object required: false headers: [] jsonPayloadSchema: type: object properties: requestId: type: *ref_0 x-parser-schema-id: event: type: string enum: - LastBarUpdate - MCapBarUpdate x-parser-schema-id: messageType: type: string x-parser-schema-id: data: type: object x-parser-schema-id: x-parser-schema-id: ChartsOutgoingMessage title: Charts bar update example: No examples found bindings: [] extensions: - id: x-parser-unique-object-id value: Outgoing bindings: [] extensions: *ref_1 sendOperations: - *ref_2 receiveOperations: - *ref_3 sendMessages: - *ref_4 receiveMessages: - *ref_5 - *ref_6 extensions: - id: x-parser-unique-object-id value: charts securitySchemes: [] ````