MCP TypeScript SDK (V2) / @modelcontextprotocol/client / client/stdio

client/stdio

Classes

StdioClientTransport

Defined in: packages/client/src/client/stdio.ts:101

Client transport for stdio: this will connect to a server by spawning a process and communicating with it over stdin/stdout.

This transport is only available in Node.js environments.

Implements

• Transport

Constructors

Constructor

new StdioClientTransport(server): StdioClientTransport

Defined in: packages/client/src/client/stdio.ts:111

Parameters

server

StdioServerParameters

Returns

StdioClientTransport

Properties

onclose?

optional onclose?: () => void

Defined in: packages/client/src/client/stdio.ts:107

Callback for when the connection is closed for any reason.

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

Returns

void

Implementation of

Transport.onclose

onerror?

optional onerror?: (error) => void

Defined in: packages/client/src/client/stdio.ts:108

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.

Parameters

error

Error

Returns

void

Implementation of

Transport.onerror

onmessage?

optional onmessage?: (message) => void

Defined in: packages/client/src/client/stdio.ts:109

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

Includes the request and authInfo if the transport is authenticated.

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

Parameters

message

JSONRPCMessage

Returns

void

Implementation of

Transport.onmessage

Accessors

pid

Get Signature

get pid(): number | null

Defined in: packages/client/src/client/stdio.ts:200

The child process pid spawned by this transport.

This is only available after the transport has been started.

Returns

number | null

stderr

Get Signature

get stderr(): Stream | null

Defined in: packages/client/src/client/stdio.ts:187

The stderr stream of the child process, if StdioServerParameters.stderr was set to "pipe" or "overlapped".

If stderr piping was requested, a PassThrough stream is returned immediately, allowing callers to attach listeners before the start method is invoked. This prevents loss of any early error output emitted by the child process.

Returns

Stream | null

Methods

close()

close(): Promise<void>

Defined in: packages/client/src/client/stdio.ts:219

Closes the connection.

Returns

Promise<void>

Implementation of

Transport.close

send()

send(message): Promise<void>

Defined in: packages/client/src/client/stdio.ts:260

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

message

JSONRPCMessage

Returns

Promise<void>

Implementation of

Transport.send

start()

start(): Promise<void>

Defined in: packages/client/src/client/stdio.ts:122

Starts the server process and prepares to communicate with it.

Returns

Promise<void>

Implementation of

Transport.start

Type Aliases

StdioServerParameters

StdioServerParameters = object

Defined in: packages/client/src/client/stdio.ts:10

Properties

args?

optional args?: string[]

Defined in: packages/client/src/client/stdio.ts:19

Command line arguments to pass to the executable.

command

command: string

Defined in: packages/client/src/client/stdio.ts:14

The executable to run to start the server.

cwd?

optional cwd?: string

Defined in: packages/client/src/client/stdio.ts:40

The working directory to use when spawning the process.

If not specified, the current working directory will be inherited.

env?

optional env?: Record<string, string>

Defined in: packages/client/src/client/stdio.ts:26

The environment to use when spawning the process.

If not specified, the result of getDefaultEnvironment will be used.

maxBufferSize?

optional maxBufferSize?: number

Defined in: packages/client/src/client/stdio.ts:48

Maximum size of the read buffer in bytes. If a single message exceeds this size the transport will emit an error and close.

Defaults to 10 MB.

stderr?

optional stderr?: IOType | Stream | number

Defined in: packages/client/src/client/stdio.ts:33

How to handle stderr of the child process. This matches the semantics of Node's child_process.spawn.

The default is "inherit", meaning messages to stderr will be printed to the parent process's stderr.

Variables

DEFAULT_INHERITED_ENV_VARS

const DEFAULT_INHERITED_ENV_VARS: string[]

Defined in: packages/client/src/client/stdio.ts:54

Environment variables to inherit by default, if an environment is not explicitly given.

Functions

getDefaultEnvironment()

getDefaultEnvironment(): Record<string, string>

Defined in: packages/client/src/client/stdio.ts:76

Returns a default environment object including only environment variables deemed safe to inherit.

Returns

Record<string, string>