> ## Documentation Index
> Fetch the complete documentation index at: https://cosmos-docs-cosmjs-docs.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Connection Errors

> Handle transport errors, broadcast failures, and timeouts when connecting to Cosmos chains

CosmJS surfaces errors at two levels: transport-level errors from the RPC client, and broadcast-level errors from transaction submission.

## Transport-Level Errors

| Scenario                         | Error                                                                            |
| -------------------------------- | -------------------------------------------------------------------------------- |
| Connection refused               | `Error` with `ECONNREFUSED` or `fetch failed`                                    |
| HTTP status >= 400               | `Error` with status code and response body                                       |
| JSON-RPC error response          | `Error` with serialized JSON-RPC error object                                    |
| HTTP request timeout             | `AbortError` from `fetch` (via `AbortSignal.timeout()`)                          |
| WebSocket handshake timeout      | `Error("Connection attempt timed out after X ms")`                               |
| Missing URL protocol (HTTP)      | `Error("Endpoint URL is missing a protocol. Expected 'https://' or 'http://'.")` |
| Missing URL protocol (WebSocket) | `Error("Base URL is missing a protocol. Expected 'ws://' or 'wss://'.")`         |

## Broadcast Errors

When a signed transaction is submitted but rejected during `CheckTx` (for example, insufficient fees or an invalid signature), the client throws a `BroadcastTxError`:

```typescript theme={"system"}
import { BroadcastTxError } from "@cosmjs/stargate";

try {
  await client.signAndBroadcast(address, messages, fee);
} catch (error) {
  if (error instanceof BroadcastTxError) {
    console.error("Code:", error.code, "Codespace:", error.codespace, "Log:", error.log);
  }
  throw error;
}
```

## Timeout Errors

When a transaction is submitted successfully but not included in a block before the timeout expires, the client throws a `TimeoutError` with the transaction hash:

```typescript theme={"system"}
import { TimeoutError } from "@cosmjs/stargate";

try {
  await client.signAndBroadcast(address, messages, fee);
} catch (error) {
  if (error instanceof TimeoutError) {
    console.error("Tx may still land. Hash:", error.txId);
  }
  throw error;
}
```

<Warning>
  A `TimeoutError` does not mean the transaction failed — it may still be included in a later block. You can query for it later using `client.getTx(error.txId)`.
</Warning>

## Fire-and-Forget Broadcasting

If you don't want to wait for block inclusion, use `signAndBroadcastSync` to get the transaction hash immediately after submission:

```typescript theme={"system"}
const txHash = await client.signAndBroadcastSync(address, messages, fee);
```

This avoids the polling loop and the `TimeoutError` entirely. Use it when your application handles confirmation tracking separately.

## No Built-In Retry

Neither `HttpClient` nor `HttpBatchClient` retry failed requests. If your application needs retry logic for transient network errors, wrap the RPC client or implement retries at the application level.

## Next Steps

<CardGroup cols={2}>
  <Card title="Timeouts" icon="clock" href="/cosmjs/v0.38.x/guides/connect/timeouts">
    Configure timeout values to tune error behavior.
  </Card>

  <Card title="Connect to a Chain" icon="link" href="/cosmjs/v0.38.x/guides/connect/connect">
    Return to the connection overview.
  </Card>
</CardGroup>