> ## Documentation Index
> Fetch the complete documentation index at: https://praison.ai/docs/llms.txt
> Use this file to discover all available pages before exploring further.
# MCP STDIO Server Transport
> The STDIO transport that powers 'praisonai-mcp serve --transport stdio'
The STDIO server transport lets `praisonai-mcp` talk to Claude Desktop, Cursor, and Windsurf over stdin/stdout โ reliably, on every platform.
```mermaid theme={"theme":{"light":"vitesse-light","dark":"vitesse-dark"}}
graph LR
Client[๐ MCP Client] --> Stdin[๐ฅ stdin
byte lines]
Stdin --> Reader[๐งต mcp-stdio-reader
thread]
Reader --> Queue[๐ฆ bounded queue
maxsize 1000]
Queue --> Loop[โ๏ธ asyncio loop]
Loop --> Handler[๐ค server handler]
Handler --> Stdout[๐ค stdout buffer]
classDef input fill:#8B0000,stroke:#7C90A0,color:#fff
classDef process fill:#189AB4,stroke:#7C90A0,color:#fff
classDef config fill:#6366F1,stroke:#7C90A0,color:#fff
classDef output fill:#10B981,stroke:#7C90A0,color:#fff
class Client,Stdin input
class Reader,Loop,Handler process
class Queue config
class Stdout output
```
## Quick Start
```bash theme={"theme":{"light":"vitesse-light","dark":"vitesse-dark"}}
pip install "praisonai-mcp"
```
```bash theme={"theme":{"light":"vitesse-light","dark":"vitesse-dark"}}
praisonai-mcp serve --transport stdio
```
Works on Linux, macOS, and Windows โ including Windows + Python 3.13.
```json theme={"theme":{"light":"vitesse-light","dark":"vitesse-dark"}}
{
"mcpServers": {
"praisonai": {
"command": "praisonai-mcp",
"args": ["serve", "--transport", "stdio"]
}
}
}
```
***
## How It Works
The host reads stdin on a dedicated thread and hands lines to the asyncio loop, so the async pipe API is never touched.
```mermaid theme={"theme":{"light":"vitesse-light","dark":"vitesse-dark"}}
sequenceDiagram
participant Client
participant Stdin as stdin.buffer
participant Reader as mcp-stdio-reader thread
participant Queue as queue.Queue(maxsize=1000)
participant Loop as asyncio loop
participant Server as server.handle_message
participant Stdout as sys.stdout.buffer
Client->>Stdin: JSON-RPC line (bytes)
Stdin->>Reader: read line
Reader->>Queue: put(line) โ backpressure if full
Loop->>Queue: run_in_executor(get)
Queue-->>Loop: line
Loop->>Server: handle_message(parsed)
Server-->>Loop: response
Loop->>Stdout: write(response) + flush
Stdout-->>Client: JSON-RPC response
```
Reading stdin on a background thread โ instead of `loop.connect_read_pipe(sys.stdin)` โ is why the host runs on Windows `ProactorEventLoop` + Python 3.13, where the async pipe API raises `OSError: [WinError 6] The handle is invalid`.
***
## Reliability Guarantees
| Guarantee | What it means |
| --------------------------- | ------------------------------------------------------------------------------------------------------------------------- |
| **Cross-platform** | Runs on Linux, macOS, and Windows (including Windows + Python 3.13, previously broken). |
| **Malformed input is safe** | Non-UTF-8 or invalid JSON becomes a JSON-RPC `-32700` parse error; the server keeps running. |
| **Bounded memory** | The stdin queue is capped at `1000` lines with backpressure, so a fast or hostile client can't grow memory without limit. |
| **Clean shutdown** | `stop()` wakes a reader blocked on idle-but-open stdin, so Ctrl+C and client disconnect never hang. |
A malformed line produces this response, and the transport continues:
```json theme={"theme":{"light":"vitesse-light","dark":"vitesse-dark"}}
{"jsonrpc": "2.0", "id": null, "error": {"code": -32700, "message": "Parse error: ..."}}
```
***
## Best Practices
STDIO transport runs the same on Linux, macOS, and Windows. On Windows it works under the `ProactorEventLoop` on Python 3.13 โ no workarounds needed.
The intake queue is fixed at `1000` lines. When it fills, the reader thread applies backpressure until the loop drains it โ the server stays responsive instead of buffering without limit.
Invalid UTF-8 or bad JSON is reported as a JSON-RPC `-32700` parse error. The server logs it to stderr and keeps serving; it never exits on bad bytes.
When stdin closes (client disconnect) or you press Ctrl+C, `stop()` enqueues an EOF sentinel that unblocks the reader, so `run()` exits cleanly without hanging.
***
## Related
Heavy MCP host reference and client setup.
All MCP transport mechanisms compared.
Standalone host package guide.
Run the MCP host on Windows.