---
title: "Transports"
description: "The transport layer that moves JSON-RPC between dApps and wallets."
url: "https://sigilry.org/concepts/transports"
---

Transports are responsible for delivering JSON-RPC requests and responses between the dApp and the wallet extension.

## Core interface

```ts
import type { RequestPayload, ResponsePayload } from "@sigilry/dapp/messages";

export interface RpcTransport {
  submit(payload: RequestPayload): Promise<ResponsePayload>;
}
```

## WindowTransport

`WindowTransport` uses `window.postMessage` for cross-context communication.

```ts
import { createCantonClient, WindowTransport } from "@sigilry/dapp";

async function getStatus() {
  const transport = new WindowTransport(window, {
    timeout: 30000,
    targetOrigin: "*",
  });

  const client = createCantonClient(transport);
  return await client.status();
}

getStatus().then(console.log);
```

### Options

* `timeout`: request timeout in milliseconds (default `30000`).
* `targetOrigin`: `postMessage` target origin (default `*`).
* `target`: optional routing key that addresses one wallet extension when several are installed (default unset). Providers from [discovery](../discovery/) set it from the wallet’s announcement.

## WalletConnectTransport

`WalletConnectTransport` carries the same JSON-RPC surface over the WalletConnect relay instead of `postMessage`, for WalletConnect-capable Canton wallets (cross-device, no extension). It requires a WalletConnect Cloud `projectId` and dApp `metadata`; see the [API reference](../../api-reference/dapp/src/classes/walletconnecttransport/) for the full `WalletConnectTransportConfig`.

## Custom transports

`@sigilry/dapp` ships only `WindowTransport` and `WalletConnectTransport`. For other environments (HTTP, WebSocket, iframe bridges), implement `RpcTransport` yourself. A minimal HTTP example:

```ts
import type { RequestPayload, ResponsePayload } from "@sigilry/dapp/messages";
import type { RpcTransport } from "@sigilry/dapp/transport";

export class HttpTransport implements RpcTransport {
  constructor(private readonly baseUrl: string) {}

  async submit(payload: RequestPayload): Promise<ResponsePayload> {
    const response = await fetch(`${this.baseUrl}/rpc`, {
      method: "POST",
      headers: { "content-type": "application/json" },
      body: JSON.stringify(payload),
    });

    if (!response.ok) {
      throw new Error(`HTTP ${response.status}`);
    }

    return (await response.json()) as ResponsePayload;
  }
}
```