WebSocket Link

wsLink is a terminating link that's used when using tRPC's WebSockets Client and Subscriptions, which you can learn more about here.

Usage

To use wsLink, you need to pass it a TRPCWebSocketClient, which you can create with createWSClient:

client/index.ts
ts
import { createTRPCClient, createWSClient, wsLink } from '@trpc/client';
import type { AppRouter } from '../server';
const wsClient = createWSClient({
  url: 'ws://localhost:3000',
});
const trpcClient = createTRPCClient<AppRouter>({
  links: [wsLink<AppRouter>({ client: wsClient })],
});

client/index.ts
ts
import { createTRPCClient, createWSClient, wsLink } from '@trpc/client';
import type { AppRouter } from '../server';
const wsClient = createWSClient({
  url: 'ws://localhost:3000',
});
const trpcClient = createTRPCClient<AppRouter>({
  links: [wsLink<AppRouter>({ client: wsClient })],
});

wsLink Options

The wsLink function requires a TRPCWebSocketClient to be passed, which can be configured with the fields defined in WebSocketClientOptions:

ts
export interface WebSocketLinkOptions {
  client: TRPCWebSocketClient;
  /**
   * Data transformer
   * @link https://trpc.io/docs/v11/data-transformers
   **/
  transformer?: DataTransformerOptions;
}
function createWSClient(opts: WebSocketClientOptions) => TRPCWebSocketClient
export interface WebSocketClientOptions {
  /**
   * The URL to connect to (can be a function that returns a URL)
   */
  url: string | (() => MaybePromise<string>);
  /**
   * Ponyfill which WebSocket implementation to use
   */
  WebSocket?: typeof WebSocket;
  /**
   * The number of milliseconds before a reconnect is attempted.
   * @default {@link exponentialBackoff}
   */
  retryDelayMs?: typeof exponentialBackoff;
  /**
   * Triggered when a WebSocket connection is established
   */
  onOpen?: () => void;
  /**
   * Triggered when a WebSocket connection is closed
   */
  onClose?: (cause?: { code?: number }) => void;
  /**
   * Lazy mode will close the WebSocket automatically after a period of inactivity (no messages sent or received and no pending requests)
   */
  lazy?: {
    /**
     * Enable lazy mode
     * @default false
     */
    enabled: boolean;
    /**
     * Close the WebSocket after this many milliseconds
     * @default 0
     */
    closeMs: number;
  };
}

ts
export interface WebSocketLinkOptions {
  client: TRPCWebSocketClient;
  /**
   * Data transformer
   * @link https://trpc.io/docs/v11/data-transformers
   **/
  transformer?: DataTransformerOptions;
}
function createWSClient(opts: WebSocketClientOptions) => TRPCWebSocketClient
export interface WebSocketClientOptions {
  /**
   * The URL to connect to (can be a function that returns a URL)
   */
  url: string | (() => MaybePromise<string>);
  /**
   * Ponyfill which WebSocket implementation to use
   */
  WebSocket?: typeof WebSocket;
  /**
   * The number of milliseconds before a reconnect is attempted.
   * @default {@link exponentialBackoff}
   */
  retryDelayMs?: typeof exponentialBackoff;
  /**
   * Triggered when a WebSocket connection is established
   */
  onOpen?: () => void;
  /**
   * Triggered when a WebSocket connection is closed
   */
  onClose?: (cause?: { code?: number }) => void;
  /**
   * Lazy mode will close the WebSocket automatically after a period of inactivity (no messages sent or received and no pending requests)
   */
  lazy?: {
    /**
     * Enable lazy mode
     * @default false
     */
    enabled: boolean;
    /**
     * Close the WebSocket after this many milliseconds
     * @default 0
     */
    closeMs: number;
  };
}

Reference

You can check out the source code for this link on GitHub.