Struct MessageDispatcher

pub struct MessageDispatcher<R> { /* private fields */ }

Provides a dispatcher for sending MCP messages and handling responses.

MessageDispatcher facilitates MCP communication by managing message sending, request tracking, and response handling. It supports both client-to-server and server-to-client message flows through implementations of the McpDispatch trait. The dispatcher uses a transport mechanism (e.g., stdin/stdout) to serialize and send messages, and it tracks pending requests with a configurable timeout mechanism for asynchronous responses.

Implementations

impl<R> MessageDispatcher<R>

pub fn new( pending_requests: Arc<Mutex<HashMap<RequestId, Sender<R>>>>, writable_std: Mutex<Pin<Box<dyn AsyncWrite + Sync + Send>>>, message_id_counter: Arc<AtomicI64>, request_timeout: Duration, ) -> MessageDispatcher<R>

Creates a new MessageDispatcher instance with the given configuration.

Arguments

• pending_requests - A thread-safe map for storing pending request IDs and their response channels.
• writable_std - A mutex-protected, pinned writer (e.g., stdout) for sending serialized messages.
• message_id_counter - An atomic counter for generating unique request IDs.
• request_timeout - The timeout duration in milliseconds for awaiting responses.

Returns

A new MessageDispatcher instance configured for MCP message handling.

pub fn request_id_for_message( &self, message: &impl McpMessage, request_id: Option<RequestId>, ) -> Option<RequestId>

Determines the request ID for an outgoing MCP message.

For requests, generates a new ID using the internal counter. For responses or errors, uses the provided request_id. Notifications receive no ID.

Arguments

• message - The MCP message to evaluate.
• request_id - An optional existing request ID (required for responses/errors).

Returns

An Option<RequestId>: Some for requests or responses/errors, None for notifications.

pub fn next_request_id(&self) -> RequestId

Trait Implementations

impl McpDispatch<ClientMessages, ServerMessages, ClientMessage, ServerMessage> for MessageDispatcher<ClientMessage>

fn send_message<'life0, 'async_trait>( &'life0 self, messages: ServerMessages, request_timeout: Option<Duration>, ) -> Pin<Box<dyn Future<Output = Result<Option<ClientMessages>, TransportError>> + Send + 'async_trait>>

where 'life0: 'async_trait, MessageDispatcher<ClientMessage>: 'async_trait,

Sends a message from the server to the client and awaits a response if applicable.

Serializes the ServerMessages to JSON, writes it to the transport, and waits for a ClientMessages response if the message is a request. Notifications and responses return Ok(None).

Arguments

• messages - The client message to send, coulld be a single message or batch.

Returns

A TransportResult containing Some(ClientMessages) for requests with a response, or None for notifications/responses, or an error if the operation fails.

Errors

Returns a TransportError if serialization, writing, or timeout occurs.

fn write_str<'life0, 'life1, 'async_trait>( &'life0 self, payload: &'life1 str, ) -> Pin<Box<dyn Future<Output = Result<(), TransportError>> + Send + 'async_trait>>

where 'life0: 'async_trait, 'life1: 'async_trait, MessageDispatcher<ClientMessage>: 'async_trait,

Writes a string payload to the underlying asynchronous writable stream, appending a newline character and flushing the stream afterward.

fn send<'life0, 'async_trait>( &'life0 self, message: ServerMessage, request_timeout: Option<Duration>, ) -> Pin<Box<dyn Future<Output = Result<Option<ClientMessage>, TransportError>> + Send + 'async_trait>>

where 'life0: 'async_trait, MessageDispatcher<ClientMessage>: 'async_trait,

fn send_batch<'life0, 'async_trait>( &'life0 self, message: Vec<ServerMessage>, request_timeout: Option<Duration>, ) -> Pin<Box<dyn Future<Output = Result<Option<Vec<ClientMessage>>, TransportError>> + Send + 'async_trait>>

where 'life0: 'async_trait, MessageDispatcher<ClientMessage>: 'async_trait,

impl McpDispatch<ServerMessages, ClientMessages, ServerMessage, ClientMessage> for MessageDispatcher<ServerMessage>

fn send_message<'life0, 'async_trait>( &'life0 self, messages: ClientMessages, request_timeout: Option<Duration>, ) -> Pin<Box<dyn Future<Output = Result<Option<ServerMessages>, TransportError>> + Send + 'async_trait>>

where 'life0: 'async_trait, MessageDispatcher<ServerMessage>: 'async_trait,

Sends a message from the client to the server and awaits a response if applicable.

Serializes the ClientMessages to JSON, writes it to the transport, and waits for a ServerMessages response if the message is a request. Notifications and responses return Ok(None).

Arguments

• messages - The client message to send, coulld be a single message or batch.

Returns

A TransportResult containing Some(ServerMessages) for requests with a response, or None for notifications/responses, or an error if the operation fails.

Errors

Returns a TransportError if serialization, writing, or timeout occurs.

fn write_str<'life0, 'life1, 'async_trait>( &'life0 self, payload: &'life1 str, ) -> Pin<Box<dyn Future<Output = Result<(), TransportError>> + Send + 'async_trait>>

where 'life0: 'async_trait, 'life1: 'async_trait, MessageDispatcher<ServerMessage>: 'async_trait,

Writes a string payload to the underlying asynchronous writable stream, appending a newline character and flushing the stream afterward.

fn send<'life0, 'async_trait>( &'life0 self, message: ClientMessage, request_timeout: Option<Duration>, ) -> Pin<Box<dyn Future<Output = Result<Option<ServerMessage>, TransportError>> + Send + 'async_trait>>

where 'life0: 'async_trait, MessageDispatcher<ServerMessage>: 'async_trait,

fn send_batch<'life0, 'async_trait>( &'life0 self, message: Vec<ClientMessage>, request_timeout: Option<Duration>, ) -> Pin<Box<dyn Future<Output = Result<Option<Vec<ServerMessage>>, TransportError>> + Send + 'async_trait>>

where 'life0: 'async_trait, MessageDispatcher<ServerMessage>: 'async_trait,