# Connect to a Core

> Connect and authenticate a Python or TypeScript client with a Synnax Core: connect to Synnax Desktop, log in with arguments or sy login, use TLS, and close the client.

Create a client to connect your code to a Synnax Core. The client logs in with the username and password of a [user](https://docs.synnaxlabs.com/reference/enterprise/users) on the Core.

## Connect to Synnax Desktop

Scripts on the same computer as Synnax Desktop can connect to its Core while it runs. Synnax Desktop saves the address of its Core and an API key in `~/.synnax/desktop.json`, which only your user can read. The Python client reads this file when you give no arguments:

```python
import synnax as sy

client = sy.Synnax()
```

To get the code for each client, click the code button in the top bar of Synnax Desktop, or run the **Connect from code** command. The dialog shows the install command that matches the version of Synnax Desktop, and code that you can copy. The **TypeScript** tab gives code with the address and the API key filled in. Other clients, such as C++ and LabVIEW, can use the host, the port, and the API key from that code.

When you close Synnax Desktop, its Core stops, and the connected scripts lose their connection. The API key stays the same the next time you open it. The port also stays the same, unless another program uses it.

To stop every script that uses the key, click **Reset key** in the dialog. Python scripts that call `sy.Synnax()` use the new key the next time they start. Code that holds the old key needs the new one. **Erase all data** also deletes the key.

## Connect with arguments

[Enterprise](https://docs.synnaxlabs.com/reference/get-started/editions "Needs Synnax Enterprise")

**Python**

```python
import synnax as sy

client = sy.Synnax(
    host="core.example.com",
    port=9090,
    username="operator",
    password="secret",
)
```

The client logs in when you create it. It raises `sy.AuthError` when the credentials are wrong. It raises `Unreachable`, from the `freighter` package, when it cannot reach the Core.

**TypeScript**

```typescript
import { Synnax } from "@synnaxlabs/client";

const client = new Synnax({
  host: "core.example.com",
  port: 9090,
  username: "operator",
  password: "secret",
});
await client.connect();
```

The client starts to connect when you create it, but it does not wait. `connect` waits for the connection. It throws `AuthError` when the credentials are wrong, and `DisconnectedError` when it cannot reach the Core. Without `connect`, the first request throws the same errors.

To keep credentials out of a script, read them from environment variables that you set. The clients read no environment variables by themselves.

## Log in once with sy login

The `sy login` command saves your credentials, so Python scripts can connect with no arguments. It is part of the Python client. Run it in a terminal:

```bash
sy login
```

Answer the prompts. Press **Enter** to keep the default in parentheses:

```plaintext
Enter your Synnax connection parameters:
Host (localhost): core.example.com
Port (9090):
Username (synnax): operator
Password:
Secure Connection? [y/n] (n):
```

When you answer `y` to the secure prompt, the command also asks for the “CA certificate path”. Enter the path to the `ca.crt` file of the Core. Leave it empty when the Core has a certificate from a public authority.

The command connects to the Core, then prints “Connection successful!”. In your scripts, create the client with no arguments:

```python
import synnax as sy

client = sy.Synnax()
```

The command stores the host, port, username, TLS setting, and CA certificate path in `~/.synnax/config.json`. It stores the password in the keychain of your operating system, under the name `synnax`. When the login fails, the command saves nothing. Run `sy login` again to change the values.

With no saved login, `sy.Synnax()` connects to [Synnax Desktop](https://docs.synnaxlabs.com/reference/client/connect#connect-to-synnax-desktop). When neither is saved, it raises `sy.ValidationError`. When you give no host, the client ignores the other arguments and uses the saved login.

## Connect with TLS

When the Core serves TLS, set `secure` to true. For how to give the Core a certificate, see [Set up TLS](https://docs.synnaxlabs.com/reference/enterprise/tls).

[Enterprise](https://docs.synnaxlabs.com/reference/get-started/editions "Needs Synnax Enterprise")

**Python**

```python
client = sy.Synnax(
    host="core.example.com",
    port=9090,
    username="operator",
    password="secret",
    secure=True,
)
```

The Python client checks the certificate of the Core, and checks that the certificate is for the host that you connect to. A certificate from a public authority, such as Let’s Encrypt, needs no setup. When the Core uses a self-signed certificate, give the path to its CA certificate in `ca_cert`:

```python
client = sy.Synnax(
    host="core.example.com",
    port=9090,
    username="operator",
    password="secret",
    secure=True,
    ca_cert="/path/to/ca.crt",
)
```

A Core that you start with `--auto-cert` makes its own CA certificate. Give its path in `ca_cert`, or save it with [`sy login`](https://docs.synnaxlabs.com/reference/client/connect#log-in-once-with-sy-login). To find the file, see [Copy the CA certificate](https://docs.synnaxlabs.com/reference/enterprise/certificates#copy-the-ca-certificate).

**TypeScript**

```typescript
const client = new Synnax({
  host: "core.example.com",
  port: 9090,
  username: "operator",
  password: "secret",
  secure: true,
});
```

The TypeScript client checks the certificate of the Core. When the Core uses a self-signed certificate, the computer must trust its CA certificate. The TypeScript client has no CA certificate option. In a browser, [install the CA certificate](https://docs.synnaxlabs.com/reference/enterprise/certificates) on the computer. For Node.js, see [Node.js](https://docs.synnaxlabs.com/reference/enterprise/certificates#nodejs).

## Close the client

Close the client when your code is done with it:

[Enterprise](https://docs.synnaxlabs.com/reference/get-started/editions "Needs Synnax Enterprise")

**Python**

```python
client.close()
```

When the script exits, the client closes by itself.

**TypeScript**

```typescript
await client.close();
```

A Node.js script does not exit until you close the client.

## Client options

[Enterprise](https://docs.synnaxlabs.com/reference/get-started/editions "Needs Synnax Enterprise")

**Python**

* [`host`](https://docs.synnaxlabs.com/reference/client/connect#python-host)`str`

  The hostname or IP address of the Core. With no host, the client uses the values that `sy login` saved.

* [`port`](https://docs.synnaxlabs.com/reference/client/connect#python-port)`int`

  The port of the Core.

* [`username`](https://docs.synnaxlabs.com/reference/client/connect#python-username)`str`

  The username to log in with.

* [`password`](https://docs.synnaxlabs.com/reference/client/connect#python-password)`str`

  The password to log in with.

* [`secure`](https://docs.synnaxlabs.com/reference/client/connect#python-secure)`bool = False`

  Connect with TLS.

* [`ca_cert`](https://docs.synnaxlabs.com/reference/client/connect#python-ca-cert)`str`

  The path to the CA certificate that signs the certificate of the Core. With `ca_cert` and no `secure`, the client raises `ValueError`. With no path, the client trusts the CA certificates of the computer.

* [`open_timeout`](https://docs.synnaxlabs.com/reference/client/connect#python-open-timeout)`TimeSpan = 5 s`

  How long to wait to open a connection.

* [`read_timeout`](https://docs.synnaxlabs.com/reference/client/connect#python-read-timeout)`TimeSpan = 5 s`

  How long to wait for a response.

* [`keep_alive`](https://docs.synnaxlabs.com/reference/client/connect#python-keep-alive)`TimeSpan = 30 s`

  How often an async streamer checks its connection to the Core.

* [`max_retries`](https://docs.synnaxlabs.com/reference/client/connect#python-max-retries)`int = 3`

  How many times to retry a request that fails to reach the Core.

* [`clock_skew_threshold`](https://docs.synnaxlabs.com/reference/client/connect#python-clock-skew-threshold)`TimeSpan = 1 s`

  The largest difference between the clocks of the computer and the Core before the client prints a warning.

**TypeScript**

* [`host`](https://docs.synnaxlabs.com/reference/client/connect#typescript-host)`string`

  The hostname or IP address of the Core.

* [`port`](https://docs.synnaxlabs.com/reference/client/connect#typescript-port)`number | string`

  The port of the Core.

* [`username`](https://docs.synnaxlabs.com/reference/client/connect#typescript-username)`string`

  The username to log in with.

* [`password`](https://docs.synnaxlabs.com/reference/client/connect#typescript-password)`string`

  The password to log in with.

* [`secure`](https://docs.synnaxlabs.com/reference/client/connect#typescript-secure)`boolean = false`

  Connect with TLS.

* [`connectivityPollFrequency`](https://docs.synnaxlabs.com/reference/client/connect#typescript-connectivity-poll-frequency)`TimeSpan = 30 s`

  How often the client checks that it can reach the Core.

* [`clockSkewThreshold`](https://docs.synnaxlabs.com/reference/client/connect#typescript-clock-skew-threshold)`TimeSpan = 1 s`

  The largest difference between the clocks of the computer and the Core before the client prints a warning.

* [`name`](https://docs.synnaxlabs.com/reference/client/connect#typescript-name)`string`

  A name for the Core, which the client shows in its connection status messages.

* [`retry`](https://docs.synnaxlabs.com/reference/client/connect#typescript-retry)`object`

  How the client retries a request that fails to reach the Core: `baseInterval` (1 s), `maxInterval`, `maxRetries` (5), `scale` (1), and `jitter` (0).

* [`cache`](https://docs.synnaxlabs.com/reference/client/connect#typescript-cache)`boolean = true`

  Keep retrieved resources in memory and update them as they change on the Core.

* [`onRetry`](https://docs.synnaxlabs.com/reference/client/connect#typescript-on-retry)`function`

  Called each time the client retries a failed request. By default, the client logs a warning.

* [`onInternalError`](https://docs.synnaxlabs.com/reference/client/connect#typescript-on-internal-error)`function`

  Called with cache errors that have no caller to throw to. By default, the client logs the error.

When the client cannot connect, see [Troubleshooting](https://docs.synnaxlabs.com/reference/client/troubleshooting).