| ENGINE\_TYPE | string | exareme | Define the connector that should be used : **`exareme, datashield, csv, local`**. |
| ENGINE\_BASE\_URL | string | http://127.0.0.1:8080/services/ | Specify the endpoint for the data source. The parameter will be provided for the connector. |
| TOS\_SKIP | boolean | false | Allow to skip the `terms of services` (this parameter is provided to the frontend) |
| GATEWAY\_PORT | number | 8081 | Indicate the port that should be used by the gateway |
| NODE\_ENV | string | dev | Value can be `prod` or `dev` |
| LOG\_LEVEL | number | 1 in production, 4 otherwise | <p>Values in range [1;4] <br>1: 'warn', 'error'<br>2: 'warn', 'error', 'log'</p><p>3: 'warn', 'error', 'log', 'verbose'<br>4: 'warn', 'error', 'log', 'verbose', 'debug'</p> |
| BASE\_URL\_CONTEXT | string | null | Define context of the gateway. E.g. `api` if the api is under `http://127.0.0.1/api/` |
| ENGINE\_TYPE | string | exareme | Define the connector that should be used : **`exareme, datashield, csv, local`**. |
| ENGINE\_BASE\_URL | string | http://127.0.0.1:8080/services/ | Specify the endpoint for the data source. The parameter will be provided for the connector. |
| TOS\_SKIP | boolean | false | Allow to skip the `terms of services` (this parameter is provided to the frontend) |
| GATEWAY\_PORT | number | 8081 | Indicate the port that should be used by the gateway |
| NODE\_ENV | string | dev | Value can be `prod` or `dev` |
| BASE\_URL\_CONTEXT | string | null | Define context of the gateway. E.g. `api` if the api is under `http://127.0.0.1/api/` |
Whenever a Frontend required a refreshToken, the gateway should tell if the user is still connected to the engine. For this, your connector should implements the function **isSessionValid**. 
{% code title="connector.interface.ts" %}
```typescript
exportinterfaceConnector{
// ...
isSessionValid?(user:User):Promise<boolean>;
// ...
}
```
{% endcode %}
This function should ensure that the user can still access the engine with the current token.
#### How to get the user 
Whether you use the local login or a 3rd party system, there is a unique way to access the user inside the Gateway. This method through the request : 
```typescript
request.user
```
This request's attribute is feed by strategy policies defined in the Gateway. Currently the following strategies are applied 
1. JWT cookies
2. JWT bearer
3. Engine (use the connector to retrieve the user)
Even if the `AUTH_SKIP` is defined you should be able to retrieve the user through the request.