Class: RubynCode::MCP::StdioTransport

Inherits:
Object
  • Object
show all
Defined in:
lib/rubyn_code/mcp/stdio_transport.rb

Overview

Communicates with an MCP server via subprocess stdin/stdout using JSON-RPC 2.0.

The server process is spawned with Open3.popen3 and kept alive for the duration of the session. Requests are written as newline-delimited JSON to stdin, and responses are read line-by-line from stdout.

Defined Under Namespace

Classes: TimeoutError, TransportError

Constant Summary collapse

DEFAULT_TIMEOUT =

seconds

30

Instance Method Summary collapse

Constructor Details

#initialize(command:, args: [], env: {}, timeout: DEFAULT_TIMEOUT) ⇒ StdioTransport

Returns a new instance of StdioTransport.

Parameters:

  • command (String) —

    executable to spawn

  • args (Array<String>) (defaults to: []) —

    arguments for the command

  • env (Hash<String, String>) (defaults to: {}) —

    additional environment variables

  • timeout (Integer) (defaults to: DEFAULT_TIMEOUT) —

    default timeout in seconds per request



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# File 'lib/rubyn_code/mcp/stdio_transport.rb', line 27

def initialize(command:, args: [], env: {}, timeout: DEFAULT_TIMEOUT)
  @command = command
  @args = args
  @env = env
  @timeout = timeout
  @request_id = 0
  @mutex = Mutex.new
  @stdin = nil
  @stdout = nil
  @stderr = nil
  @wait_thread = nil
end

Instance Method Details

#alive? ⇒ Boolean

Checks whether the subprocess is still running.

Returns:

  • (Boolean) 


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# File 'lib/rubyn_code/mcp/stdio_transport.rb', line 118

def alive?
  return false unless @wait_thread

  @wait_thread.alive?
end

#send_notification(method, params = {}) ⇒ void

This method returns an undefined value.

Sends a JSON-RPC 2.0 notification (no response expected).

Parameters:

  • method (String) —

    the JSON-RPC method name

  • params (Hash) (defaults to: {}) —

    parameters for the notification

Raises:



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# File 'lib/rubyn_code/mcp/stdio_transport.rb', line 79

def send_notification(method, params = {})
  raise TransportError, 'Transport is not running' unless alive?

  notification = {
    jsonrpc: '2.0',
    method: method,
    params: params
  }

  write_request(notification)
end

#send_request(method, params = {}) ⇒ Hash

Sends a JSON-RPC 2.0 request and waits for the correlated response.

Parameters:

  • method (String) —

    the JSON-RPC method name

  • params (Hash) (defaults to: {}) —

    parameters for the request

Returns:

  • (Hash) —

    the parsed JSON-RPC response result

Raises:



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# File 'lib/rubyn_code/mcp/stdio_transport.rb', line 59

def send_request(method, params = {})
  raise TransportError, 'Transport is not running' unless alive?

  id = next_request_id
  request = {
    jsonrpc: '2.0',
    id: id,
    method: method,
    params: params
  }

  write_request(request)
  read_response(id)
end

#start! ⇒ void

This method returns an undefined value.

Spawns the MCP server subprocess.

Raises:



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# File 'lib/rubyn_code/mcp/stdio_transport.rb', line 44

def start!
  raise TransportError, 'Transport already started' if alive?

  @stdin, @stdout, @stderr, @wait_thread = Open3.popen3(@env, @command, *@args)
rescue Errno::ENOENT => e
  raise TransportError, "Failed to start MCP server: #{e.message}"
end

#stop! ⇒ void

This method returns an undefined value.

Gracefully shuts down the MCP server and cleans up resources.



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# File 'lib/rubyn_code/mcp/stdio_transport.rb', line 94

def stop!
  return unless alive?

  begin
    send_notification('notifications/cancelled')
    @stdin&.close
  rescue IOError, Errno::EPIPE
    # Process may already be gone
  end

  begin
    @wait_thread&.join(5)
  rescue StandardError
    # Best-effort wait
  end

  force_kill if alive?
ensure
  close_streams
end