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context.dispatchWebSocketEvent

The context.dispatchWebSocketEvent function sends WebSocket events to connected clients. This enables real-time push notifications from your mim to browser or app clients.

Enable WebSocket Support

WebSocket events require WEBSOCKET_SUPPORT to be enabled when deploying your mim. See MCM Environment Variables.

Syntax​

context.dispatchWebSocketEvent(options)

Parameters​

ParameterTypeRequiredDescription
optionsobjectNoEvent configuration object

Options Object​

PropertyTypeRequiredDescription
typestringYesThe event type identifier
messagestringNoThe event payload/message

Behavior​

  • With options object: Dispatches a WebSocket event with the specified type and optional message
  • Without arguments (or null/undefined): Flushes the event queue

Examples​

Basic Event​

app.post('/notify', (request, response) => {
    context.dispatchWebSocketEvent({
        type: 'notification',
        message: 'New data available'
    });

    response.end(JSON.stringify({ sent: true }));
});

Event with JSON Payload​

app.post('/user-update', (request, response) => {
    var user = JSON.parse(request.body);

    // Save user
    context.storage.setItemWithTag('user:' + user.id, JSON.stringify(user), 'users');

    // Notify connected clients
    context.dispatchWebSocketEvent({
        type: 'user-updated',
        message: JSON.stringify({
            userId: user.id,
            timestamp: new Date().toISOString()
        })
    });

    response.end(JSON.stringify({ updated: true }));
});

Typed Events​

// Define event types as constants
var EVENT_TYPES = {
    DATA_SYNC: 'data-sync',
    STATUS_CHANGE: 'status-change',
    ERROR: 'error'
};

app.post('/sync', (request, response) => {
    // Perform sync operation...

    context.dispatchWebSocketEvent({
        type: EVENT_TYPES.DATA_SYNC,
        message: JSON.stringify({
            action: 'sync-complete',
            recordCount: 42
        })
    });

    response.end(JSON.stringify({ synced: true }));
});

Flush Event Queue​

app.post('/flush', (request, response) => {
    // Dispatch without arguments to flush the queue
    context.dispatchWebSocketEvent();

    response.end(JSON.stringify({ flushed: true }));
});

Enabling WebSocket Support​

To use dispatchWebSocketEvent, enable WebSocket support when deploying your mim:

curl -X POST http://localhost:8083/mcm/v1/containers \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $EDGE_ACCESS_TOKEN" \
  -d '{
    "name": "my-mim",
    "image": "my-mim-v1",
    "env": {
      "MCM.BASE_API_PATH": "/my-mim/v1",
      "WEBSOCKET_SUPPORT": "true"
    }
  }'

Client-Side Connection​

Clients connect to the WebSocket endpoint to receive events:

// Browser client example
const ws = new WebSocket('ws://localhost:8083/ws/my-mim/v1');

ws.onmessage = (event) => {
    const data = JSON.parse(event.data);
    console.log('Event type:', data.type);
    console.log('Message:', data.message);
};

ws.onopen = () => {
    console.log('Connected to WebSocket');
};

ws.onclose = () => {
    console.log('Disconnected from WebSocket');
};