StreamableHttpServerTransport

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

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

Parameters

configuration

Transport configuration. See Configuration for available options.

Constructors

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constructor()
constructor(enableJsonResponse: Boolean = false, enableDnsRebindingProtection: Boolean = false, allowedHosts: List<String>? = null, allowedOrigins: List<String>? = null, eventStore: EventStore? = null, retryIntervalMillis: Long? = null)

Secondary constructor for StreamableHttpServerTransport that simplifies initialization by directly taking the configurable parameters without requiring a Configuration instance.

Types

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class Configuration(val enableJsonResponse: Boolean = false, val enableDnsRebindingProtection: Boolean = false, val allowedHosts: List<String>? = null, val allowedOrigins: List<String>? = null, val eventStore: EventStore? = null, val retryInterval: Duration? = null, val maxRequestBodySize: Long = DEFAULT_MAX_REQUEST_BODY_SIZE)

Configuration options for StreamableHttpServerTransport.

Properties

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session identifier assigned after initialization, or null in stateless mode

Functions

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open suspend override fun close()
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suspend fun closeSseStream(requestId: RequestId)

Closes the SSE stream associated with the given requestId, prompting the client to reconnect. Useful for implementing polling behavior for long-running operations.

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Handles an HTTP DELETE request by closing the session and the transport.

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suspend fun handleGetRequest(session: ServerSSESession?, call: ApplicationCall)

Handles an HTTP GET request by establishing a standalone SSE stream for server-initiated notifications.

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suspend fun handlePostRequest(session: ServerSSESession?, call: ApplicationCall)

Handles POST requests containing JSON-RPC messages

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suspend fun handleRequest(session: ServerSSESession?, call: ApplicationCall)

Handles an incoming HTTP request, whether GET, POST or DELETE

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open override fun onClose(block: () -> Unit)
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open override fun onError(block: (Throwable) -> Unit)
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open override fun onMessage(block: suspend (JSONRPCMessage) -> Unit)
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open suspend override fun send(message: JSONRPCMessage, options: TransportSendOptions?)
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fun setOnSessionClosed(block: (String) -> Unit?)

A callback for session close events This is called when the server closes a session due to a DELETE request. Useful in cases when you need to clean up resources associated with the session. Note that this is different from the transport closing, if you are handling HTTP requests from multiple nodes you might want to close each StreamableHTTPServerTransport after a request is completed while still keeping the session open/running.

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A callback for session initialization events This is called when the server initializes a new session. Useful in cases when you need to register multiple mcp sessions and need to keep track of them.

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fun setSessionIdGenerator(block: () -> String?)

Function that generates a session ID for the transport. The session ID SHOULD be globally unique and cryptographically secure (e.g., a securely generated UUID, a JWT, or a cryptographic hash)

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open suspend override fun start()