WebSocket

WebSocket provides bidirectional, full-duplex communication over a single TCP connection. It's the most widely supported real-time protocol.

Try it Online

Open WebSocket Client — See WebSocket streaming in action!

Overview

Property	Value
Protocol	TCP (WebSocket)
Direction	Bidirectional
Latency	1-5ms
Reconnection	Manual
Browser Support	Universal

Endpoints

Endpoint	Description
ws://host/ws/:game	Stream by game slug
ws://host/ws/type/:type	Stream by game type

Examples

ws://localhost:3000/ws/crash
ws://localhost:3000/ws/double
ws://localhost:3000/ws/type/multiplier
wss://datastream.andrebassi.com.br/ws/crash

Message Format

Incoming Messages (Server → Client)

{
  "round_id": 512,
  "game_id": 1,
  "game_slug": "crash",
  "game_type": "multiplier",
  "finished_at": "2026-01-17T00:45:42.735266-03:00",
  "extras": "{\"point\": \"11.72\"}",
  "timestamp": 1768621542123
}

Field Descriptions

Field	Type	Description
round_id	integer	Unique round identifier
game_id	integer	Game ID in database
game_slug	string	URL-friendly game name
game_type	string	Game category
finished_at	string (ISO 8601)	Round completion time
extras	string (JSON)	Game-specific data
timestamp	integer	Unix timestamp in milliseconds

Client Implementation

JavaScript (Browser)

class WebSocketClient {
  constructor(game) {
    this.game = game;
    this.ws = null;
    this.reconnectAttempts = 0;
    this.maxReconnectAttempts = 5;
    this.reconnectDelay = 3000;
  }

  connect() {
    const protocol = window.location.protocol === 'https:' ? 'wss:' : 'ws:';
    const url = `${protocol}//${window.location.host}/ws/${this.game}`;

    this.ws = new WebSocket(url);

    this.ws.onopen = () => {
      console.log('WebSocket connected');
      this.reconnectAttempts = 0;
    };

    this.ws.onmessage = (event) => {
      const data = JSON.parse(event.data);
      this.handleMessage(data);
    };

    this.ws.onclose = () => {
      console.log('WebSocket disconnected');
      this.reconnect();
    };

    this.ws.onerror = (error) => {
      console.error('WebSocket error:', error);
    };
  }

  handleMessage(data) {
    console.log('New round:', data.round_id);
    console.log('Result:', JSON.parse(data.extras));
  }

  reconnect() {
    if (this.reconnectAttempts >= this.maxReconnectAttempts) {
      console.error('Max reconnect attempts reached');
      return;
    }

    this.reconnectAttempts++;
    console.log(`Reconnecting in ${this.reconnectDelay}ms...`);

    setTimeout(() => {
      this.connect();
    }, this.reconnectDelay);
  }

  disconnect() {
    if (this.ws) {
      this.ws.close();
    }
  }
}

// Usage
const client = new WebSocketClient('crash');
client.connect();

Go Client

package main

import (
    "encoding/json"
    "log"
    "time"

    "github.com/gorilla/websocket"
)

type Round struct {
    RoundID    int64           `json:"round_id"`
    GameSlug   string          `json:"game_slug"`
    GameType   string          `json:"game_type"`
    FinishedAt time.Time       `json:"finished_at"`
    Extras     json.RawMessage `json:"extras"`
    Timestamp  int64           `json:"timestamp"`
}

func main() {
    url := "ws://localhost:3000/ws/crash"

    c, _, err := websocket.DefaultDialer.Dial(url, nil)
    if err != nil {
        log.Fatal("dial:", err)
    }
    defer c.Close()

    for {
        _, message, err := c.ReadMessage()
        if err != nil {
            log.Println("read:", err)
            return
        }

        var round Round
        if err := json.Unmarshal(message, &round); err != nil {
            log.Println("unmarshal:", err)
            continue
        }

        log.Printf("Round %d: %s", round.RoundID, round.Extras)
    }
}

Python Client

import asyncio
import json
import websockets

async def connect():
    uri = "ws://localhost:3000/ws/crash"

    async with websockets.connect(uri) as websocket:
        print("Connected to WebSocket")

        async for message in websocket:
            data = json.loads(message)
            print(f"Round {data['round_id']}: {data['extras']}")

if __name__ == "__main__":
    asyncio.run(connect())

Server Implementation

The WebSocket handler is implemented using Fiber's WebSocket middleware:

// internal/adapters/inbound/websocket/handlers.go

func (h *Handlers) StreamByGame(c *websocket.Conn) {
    game := c.Params("game")
    ctx := context.Background()

    // Get last result and send immediately
    if latest, err := h.roundRepo.GetLatest(ctx, game); err == nil {
        data, _ := json.Marshal(latest)
        c.WriteMessage(websocket.TextMessage, data)
    }

    // Subscribe to Redis Pub/Sub
    channel := fmt.Sprintf("stream:%s", game)
    sub, err := h.subscriber.Subscribe(ctx, channel)
    if err != nil {
        return
    }

    // Stream messages
    for round := range sub {
        data, _ := json.Marshal(round)
        if err := c.WriteMessage(websocket.TextMessage, data); err != nil {
            return
        }
    }
}

Best Practices

Connection Management

1. Always implement reconnection logic - WebSocket doesn't auto-reconnect
2. Use exponential backoff - Prevent server overload during outages
3. Handle connection errors gracefully - Show user-friendly messages
4. Close connections properly - Call ws.close() when done

Message Handling

1. Parse JSON safely - Handle malformed messages
2. Validate message structure - Check required fields
3. Process messages asynchronously - Don't block the message loop
4. Buffer messages if needed - Queue for UI updates

Security

1. Use WSS (WebSocket Secure) in production
2. Validate origin header - Prevent cross-site attacks
3. Implement rate limiting - Protect against abuse
4. Authenticate connections - Use tokens in query string or first message

Troubleshooting

Connection Refused

WebSocket connection to 'ws://localhost:3000/ws/crash' failed

Solutions:

• Check if backend is running
• Verify the port is correct
• Check firewall settings

Connection Closes Immediately

WebSocket closed with code 1006

Solutions:

• Check server logs for errors
• Verify game slug exists
• Check Redis connection

Messages Not Received

Solutions:

• Verify Redis Pub/Sub is working
• Check consumer is running
• Ensure CDC pipeline is active

Performance Issues

Solutions:

• Implement message batching
• Use binary protocol for high volume
• Consider connection pooling

Comparison with Other Protocols

Feature	WebSocket	SSE	WebTransport
Bidirectional	Yes	No	Yes
Auto-reconnect	No	Yes	No
Binary data	Yes	No	Yes
Multiple streams	No	No	Yes
Proxy-friendly	Sometimes	Yes	No

When to Use WebSocket

Use WebSocket when:

• Client needs to send data to server
• Latency < 50ms is critical
• Many small messages per second
• Long-lived connections

Consider alternatives when:

• Server-only push (use SSE)
• Ultra-low latency needed (use WebTransport)
• Behind restrictive proxies (use SSE)