@modelcontextprotocol/sdk
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    Class StreamableHTTPServerTransport

    Server transport for Streamable HTTP: this implements the MCP Streamable HTTP transport specification. It supports both SSE streaming and direct HTTP responses.

    Usage example:

    // Stateful mode - server sets the session ID
    const statefulTransport = new StreamableHTTPServerTransport({
      sessionIdGenerator: () => randomUUID(),
    });

    // Stateless mode - explicitly set session ID to undefined
    const statelessTransport = new StreamableHTTPServerTransport({
      sessionIdGenerator: undefined,
    });

    // Using with pre-parsed request body
    app.post('/mcp', (req, res) => {
      transport.handleRequest(req, res, req.body);
    });

    In stateful mode:

    • Session ID is generated and included in response headers
    • Session ID is always included in initialization responses
    • Requests with invalid session IDs are rejected with 404 Not Found
    • Non-initialization requests without a session ID are rejected with 400 Bad Request
    • State is maintained in-memory (connections, message history)

    In stateless mode:

    • No Session ID is included in any responses
    • No session validation is performed

    Implements

    Index

    Constructors

    constructor

    Properties

    onclose? onerror? onmessage? sessionId?

    Methods

    close handleRequest send start

    Constructors

    Properties

    onclose?: () => void

    Callback for when the connection is closed for any reason.

    This should be invoked when close() is called as well.

    onerror?: (error: Error) => void

    Callback for when an error occurs.

    Note that errors are not necessarily fatal; they are used for reporting any kind of exceptional condition out of band.

    onmessage?: (message: JSONRPCMessage, extra?: MessageExtraInfo) => void

    Callback for when a message (request or response) is received over the connection.

    Includes the requestInfo and authInfo if the transport is authenticated.

    The requestInfo can be used to get the original request information (headers, etc.)

    sessionId?: string

    The session ID generated for this connection.

    Methods

    • Handles an incoming HTTP request, whether GET or POST

      Parameters

      • req: IncomingMessage & { auth?: AuthInfo }
      • res: ServerResponse
      • OptionalparsedBody: unknown

      Returns Promise<void>

    • Sends a JSON-RPC message (request or response).

      If present, relatedRequestId is used to indicate to the transport which incoming request to associate this outgoing message with.

      Parameters

      Returns Promise<void>

    • Starts the transport. This is required by the Transport interface but is a no-op for the Streamable HTTP transport as connections are managed per-request.

      Returns Promise<void>

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