21eef8df9a
## Motivation and Context The `MCP::Client` currently only supports HTTP transport (`MCP::Client::HTTP`). To achieve parity with other MCP SDKs (Python, TypeScript, C#) which provide stdio client transports for spawning and communicating with server subprocesses, the Ruby SDK needs a stdio client transport. https://modelcontextprotocol.io/specification/2025-11-25/basic/transports#stdio This enables building MCP clients that launch server processes and communicate via stdin/stdout using newline-delimited JSON-RPC 2.0 messages. ## How Has This Been Tested? Added tests for process spawning, protocol initialization handshake, notification handling, error handling, and transport close lifecycle. ## Additional context Enabled the `Lint/IncompatibleIoSelectWithFiberScheduler` cop in `.rubocop.yml` to detect accidental use of `IO.select` instead of `IO#wait_readable`.
58 lines
1.8 KiB
Ruby
58 lines
1.8 KiB
Ruby
# frozen_string_literal: true
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$LOAD_PATH.unshift(File.expand_path("../lib", __dir__))
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require "mcp"
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require "json"
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# Simple stdio client example that connects to the stdio_server.rb example
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# Usage: ruby examples/stdio_client.rb
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server_script = File.expand_path("stdio_server.rb", __dir__)
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transport = MCP::Client::Stdio.new(command: "ruby", args: [server_script])
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client = MCP::Client.new(transport: transport)
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begin
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# List available tools
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puts "=== Listing tools ==="
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tools = client.tools
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tools.each do |tool|
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puts " Tool: #{tool.name} - #{tool.description}"
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end
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# Call the example_tool (adds two numbers)
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puts "\n=== Calling tool: example_tool ==="
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tool = tools.find { |t| t.name == "example_tool" }
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response = client.call_tool(tool: tool, arguments: { a: 5, b: 3 })
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puts " Response: #{JSON.pretty_generate(response.dig("result", "content"))}"
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# Call the echo tool
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puts "\n=== Calling tool: echo ==="
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tool = tools.find { |t| t.name == "echo" }
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response = client.call_tool(tool: tool, arguments: { message: "Hello from stdio client!" })
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puts " Response: #{JSON.pretty_generate(response.dig("result", "content"))}"
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# List prompts
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puts "\n=== Listing prompts ==="
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prompts = client.prompts
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prompts.each do |prompt|
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puts " Prompt: #{prompt["name"]} - #{prompt["description"]}"
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end
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# List resources
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puts "\n=== Listing resources ==="
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resources = client.resources
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resources.each do |resource|
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puts " Resource: #{resource["name"]} (#{resource["uri"]})"
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end
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# Read a resource
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puts "\n=== Reading resource: https://test_resource.invalid ==="
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contents = client.read_resource(uri: "https://test_resource.invalid")
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puts " Response: #{JSON.pretty_generate(contents)}"
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rescue => e
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puts "Error: #{e.message}"
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puts e.backtrace.first(5).join("\n")
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ensure
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transport.close
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end
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