turbomcp-stdio

Standard I/O transport implementation for the TurboMCP Model Context Protocol SDK.

Overview

This crate provides the StdioTransport implementation for MCP communication over stdin/stdout, which is the standard way MCP servers communicate with clients. It supports JSON-RPC over newline-delimited JSON.

MCP Specification Compliance

This implementation is fully compliant with the MCP stdio transport specification (2025-06-18):

• Newline-delimited JSON: Uses LinesCodec for proper message framing
• No embedded newlines: Validates messages don't contain \n or \r characters
• UTF-8 encoding: All messages are UTF-8 encoded
• stderr for logging: Uses tracing crate which outputs to stderr by default
• Bidirectional communication: Supports both client→server and server→client messages
• Valid JSON only: Validates all messages are well-formed JSON before sending

Usage

use turbomcp_stdio::{StdioTransport, Transport};

#[tokio::main]
async fn main() {
    let transport = StdioTransport::new();
    transport.connect().await.unwrap();

    // Send and receive messages...
}

Features

• Zero-copy message handling with Bytes
• Lock-free atomic metrics for high performance
• Background reader task with bounded channel for backpressure
• Configurable message size limits

Architecture

The transport follows the hybrid mutex pattern for optimal async performance:

• std::sync::Mutex for state/config (short-lived locks, never cross .await)
• AtomicMetrics for lock-free counter updates
• tokio::sync::Mutex for I/O streams (necessary for async I/O)

License

MIT