SignalR hub configuration in Vue application

18 Nov 201814 minutes to read

Overview

This guide explains how to configure SignalR Hub in a Vue application for real-time collaborative diagram editing.

Prerequisites

How to create Vue sample

To create a Vue application, follow the steps outlined in the Vue Getting Started documentation.

How to add packages in the Vue application

Open the terminal and install the following packages using npm.

  • @microsoft/signalr
  • @syncfusion/ej2-vue-diagrams

Configure SignalR service in Vue application

To enable real-time collaboration, configure SignalR HubConnection in your Vue component as follows:

  • Initialize the HubConnection within a onMounted life cycle hook and start it using start().
  • Connect to the /diagramHub endpoint with WebSocket transport skipNegotiation: true and enable automatic reconnect to handle transient network issues.
  • Subscribe to the OnConnectedAsync callback to receive the unique connection ID, confirming a successful handshake with the server.
  • Join a SignalR group by calling JoinDiagram(roomName) after connecting. This ensures updates are shared only with users in the same diagram session.
  • Refer to Create Vue Simple Diagram 
<template>
  <div>
    <!-- Diagram component will be added here -->
  </div>
</template>

<script setup lang="ts">
import { ref, onMounted, onBeforeUnmount } from 'vue';
import * as signalR from '@microsoft/signalr';

const connection = ref<signalR.HubConnection | null>(null);
const roomName = ref('Syncfusion');

onMounted(() => {
  initializeSignalRConnection();
});

const initializeSignalRConnection = async () => {
  if (connection.value === null) {
    // Create connection
    const newConnection = new signalR.HubConnectionBuilder()
      .withUrl('<<Your ServiceURL>>', {
        skipNegotiation: true,
        transport: signalR.HttpTransportType.WebSockets
      })
      .withAutomaticReconnect()
      .build();

    // Triggered when the connection to the SignalR Hub is successfully established
    newConnection.on('OnConnectedAsync', (id: string) => {
      onConnectedAsync(id);
    });

    try {
      await newConnection.start();
      console.log('Connected to SignalR Hub');
      connection.value = newConnection;
    } catch (error) {
      console.error('Connection failed:', error);
    }
  }
};

const onConnectedAsync = (id: string) => {
  if (id && id.length > 0) {
    console.log('Connection ID:', id);
    // Join the room after connection is established
    connection.value?.invoke('JoinDiagram', roomName.value)
      .catch((error: Error) => {
        console.error('JoinDiagram failed:', error);
      });
  }
};

onBeforeUnmount(() => {
  if (connection.value && connection.value.state === signalR.HubConnectionState.Connected) {
    connection.value.stop();
  }
});
</script>

Notes:

  • Use a unique roomName per diagram (e.g., a diagram ID) to isolate sessions.
  • If WebSockets may be unavailable, remove SkipNegotiation so SignalR can fall back to SSE or Long Polling.
  • Consider handling reconnecting/disconnected states in the UI and securing the connection with authentication, if required.

Sending and applying real-time diagram changes

  • The Vue Diagram component triggers the historyChange event whenever the diagram is modified (e.g., add, delete, move, resize, or edit nodes/connectors).
  • Use getDiagramUpdates to produce a compact set of incremental updates (JSON-formatted changes) representing just the changes, not the entire diagram.
  • Send these changes to the hub method BroadcastToOtherUsers, which relays them to all users joined to the same SignalR group (room).
  • Each remote user listens for ReceiveData and applies the incoming changes with setDiagramUpdates, keeping their view synchronized without reloading the full diagram.
  • Enable the enableCollaborativeEditing` property on the diagram to treat multi-step edits (like drag/resize sequences or batch changes) as a single operation.
<template>
  <div>
    <DiagramComponent
      ref="diagramRef"
      id="diagram"
      width="100%"
      height="700px"
      :nodes="[]"
      :connectors="[]"
      :enableCollaborativeEditing="true"
      @historyChange="onHistoryChange"
    >
    </DiagramComponent>
  </div>
</template>

<script setup lang="ts">
import { ref, onMounted, onBeforeUnmount } from 'vue';
import { DiagramComponent } from '@syncfusion/ej2-vue-diagrams';
import * as signalR from '@microsoft/signalr';

const diagramRef = ref<InstanceType<typeof DiagramComponent> | null>(null);
const connection = ref<signalR.HubConnection | null>(null);
const roomName = ref('Syncfusion');

onMounted(() => {
  initializeConnection();
});

const initializeConnection = async () => {
  if (connection.value === null) {
    const newConnection = new signalR.HubConnectionBuilder()
      .withUrl('<<Your ServiceURL>>', {
        skipNegotiation: true,
        transport: signalR.HttpTransportType.WebSockets
      })
      .withAutomaticReconnect()
      .build();

    // Listen for remote changes from other users
    newConnection.on('ReceiveData', (diagramChanges: string[]) => {
      if (diagramChanges && diagramChanges.length > 0) {
        if (diagramRef.value && diagramRef.value.setDiagramUpdates) {
          diagramRef.value.setDiagramUpdates(diagramChanges);
        }
      }
    });

    try {
      await newConnection.start();
      console.log('Connected to SignalR Hub');
      connection.value = newConnection;
    } catch (error) {
      console.error('Connection failed:', error);
    }
  }
};

const onHistoryChange = async (args: IHistoryChangeArgs) => {
  if (args && diagramRef.value && diagramRef.value.getDiagramUpdates) {
    // Get diagram updates (incremental changes) and send to hub
    const diagramChanges = diagramRef.value.getDiagramUpdates(args);
    
    // When enableCollaborativeEditing is enabled, retrieve diagramChanges only after the group action completes.
    if (diagramChanges && diagramChanges.length > 0) {
      // Send changes to the SignalR Hub for broadcasting
      if (connection.value && connection.value.state === signalR.HubConnectionState.Connected) {
        connection.value.invoke('BroadcastToOtherUsers', diagramChanges, roomName.value)
          .catch((err: Error) => {
            console.error('Send failed:', err);
          });
      }
    }
  }
};

onBeforeUnmount(() => {
  if (connection.value && connection.value.state === signalR.HubConnectionState.Connected) {
    connection.value.stop();
  }
});
</script>

Conflict policy (optimistic concurrency) in Vue application

To maintain consistency during collaborative editing, each user applies incoming changes using setDiagramUpdates. After applying changes, the Vue sample synchronizes its userVersion with the serverVersion through the UpdateVersion event. This version-based approach ensures conflicts are resolved without locking, allowing real-time responsiveness while preserving data integrity.

Add the following code in the Vue sample application:

<template>
  <div>
    <DiagramComponent
      ref="diagramRef"
      width="100%"
      height="700px"
      :enableCollaborativeEditing="true"
      :nodes="[]"
      :connectors="[]"
      @historyChange="onHistoryChange"
    >
    </DiagramComponent>
  </div>
</template>

<script setup lang="ts">
import { ref, onMounted, onBeforeUnmount } from 'vue';
import { DiagramComponent } from '@syncfusion/ej2-vue-diagrams';
import * as signalR from '@microsoft/signalr';

const userVersion = ref<number>(0);
const diagramRef = ref<InstanceType<typeof DiagramComponent> | null>(null);
const connection = ref<signalR.HubConnection | null>(null);
const roomName = ref('Syncfusion');

onMounted(() => {
  initializeConnection();
});

const initializeConnection = async () => {
  if (connection.value === null) {
    const newConnection = new signalR.HubConnectionBuilder()
      .withUrl('<<Your ServiceURL>>', {
        skipNegotiation: true,
        transport: signalR.HttpTransportType.WebSockets
      })
      .withAutomaticReconnect()
      .build();

    // Listen for remote changes with version tracking
    newConnection.on('ReceiveData', (diagramChanges: string[], serverVersion: number) => {
      applyRemoteDiagramChanges(diagramChanges, serverVersion);
    });

    // Listen for conflict notifications
    newConnection.on('ShowConflict', () => {
      showConflict();
    });

    // Listen for explicit version updates
    newConnection.on('UpdateVersion', (serverVersion: number) => {
      updateVersion(serverVersion);
    });

    try {
      await newConnection.start();
      console.log('Connected to SignalR Hub');
      connection.value = newConnection;
    } catch (error) {
      console.error('Connection failed:', error);
    }
  }
};

const applyRemoteDiagramChanges = (diagramChanges: string[], serverVersion: number) => {
  // Sets diagram updates to current diagram
  if (diagramRef.value && diagramRef.value.setDiagramUpdates) {
    diagramRef.value.setDiagramUpdates(diagramChanges);
  }
  // Update user version to server version after applying changes
  userVersion.value = serverVersion;
};

// Capture local changes and send with version and edited IDs
const onHistoryChange = async (args: IHistoryChangeArgs) => {
  if (!diagramRef.value) {
    return;
  }

  const diagramChanges = diagramRef.value.getDiagramUpdates(args);
  if (diagramChanges && diagramChanges.length > 0) {
    const editedElements = getEditedElements(args);
    // Send changes with version and edited element IDs
    if (connection.value && connection.value.state === signalR.HubConnectionState.Connected) {
      connection.value.invoke('BroadcastToOtherUsers', diagramChanges, userVersion.value, editedElements, roomName.value)
        .catch((err: Error) => {
          console.error('Send failed:', err);
        });
    }
  }
};

const getEditedElements = (args: any): string[] => {
  // Extract and return IDs of affected nodes/connectors from args
  // TODO: implement extraction logic based on historyChange event args
  return [];
};

const updateVersion = (serverVersion: number) => {
  userVersion.value = serverVersion;
};

const showConflict = () => {
  // Show notification to inform user their update was rejected due to conflict
  const message = "Your changes conflicted with another user's updates and were not applied. Please refresh to see the latest version.";
  alert(message);
};

onBeforeUnmount(() => {
  if (connection.value && connection.value.state === signalR.HubConnectionState.Connected) {
    connection.value.stop();
  }
});
</script>