> ## Documentation Index
> Fetch the complete documentation index at: https://gofastmcp.com/llms.txt
> Use this file to discover all available pages before exploring further.
# base
# `fastmcp.client.transports.base`
## Classes
### `SessionKwargs`
Keyword arguments for the MCP ClientSession constructor.
### `ClientTransport`
Abstract base class for different MCP client transport mechanisms.
A Transport is responsible for establishing and managing connections
to an MCP server, and providing a ClientSession within an async context.
**Methods:**
#### `connect_session`
```python theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
connect_session(self, **session_kwargs: Unpack[SessionKwargs]) -> AsyncIterator[ClientSession]
```
Establishes a connection and yields an active ClientSession.
The ClientSession is *not* expected to be initialized in this context manager.
The session is guaranteed to be valid only within the scope of the
async context manager. Connection setup and teardown are handled
within this context.
**Args:**
* `**session_kwargs`: Keyword arguments to pass to the ClientSession
constructor (e.g., callbacks, timeouts).
#### `close`
```python theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
close(self)
```
Close the transport.
#### `get_session_id`
```python theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
get_session_id(self) -> str | None
```
Get the session ID for this transport, if available.