MCP Academy · 课时

使用标准输入输出运行服务器

启动服务器，让客户端可以在本地连接。

使用标准输入输出运行服务器 是 CoddyKit 上的免费 MCP Academy 课时。这是第 3 节课，共 4 节。你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。这是 MCP Academy 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 MCP Academy 课程共包含 4 节课。

本课时的部分内容尚未翻译，以英文显示。

Time to Start It Up

You have a server object and a tool. Now you need to actually run it so a client can connect and use what you built. 🏃

What stdio Means

The simplest transport is stdio: standard input and output. The client launches your script and talks to it through those two streams.

Call run()

Starting the server is one method. Calling mcp.run() hands control to FastMCP, which begins listening for messages right away.

mcp.run()

Choose the Transport

Pass a transport argument to be explicit. For local use you want "stdio", which is also the default when you call run.

mcp.run(transport="stdio")

The Main Guard

Wrap the call in the classic __main__ guard. That way the server starts only when the file is run directly, not when imported.

if __name__ == "__main__":
    mcp.run()

The Whole File

Here is a complete server: import, instance, tool, and run. Just a handful of lines and it speaks MCP.

from mcp.server.fastmcp import FastMCP
mcp = FastMCP("demo")

@mcp.tool()
def hello() -> str:
    return "Hi!"

if __name__ == "__main__":
    mcp.run()

stdout Is Reserved

One golden rule: never print to standard output. That stream carries protocol messages, and stray text will corrupt them.

Log to stderr Instead

Need to debug? Write to stderr, not stdout. The client ignores stderr, so your notes stay out of the protocol stream.

import sys
print("starting up", file=sys.stderr)

The Client Launches You

With stdio, you rarely run the script by hand. The host app starts your process for you using a configured command.

It Waits, Not Loops Idle

After run() the server blocks, waiting for messages. It isn't frozen; it's listening for the next request from the client.

stdio Is Local Only

Remember that stdio works only on the same machine, since it relies on a launched process. Remote servers use HTTP transport instead, which comes later.

Quick Check

Why must you avoid plain print() in a stdio server?

Recap

You ran the server with mcp.run() over stdio, guarded it with __main__, and kept stdout clean. It's live and listening. Let's confirm it works! ✅

常见问题解答

「使用标准输入输出运行服务器」课时是免费的吗？

是的 — 「使用标准输入输出运行服务器」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 MCP Academy 课程的其余内容，请升级到 CoddyKit PRO。 MCP Academy 课程共包含 4 节课。

「使用标准输入输出运行服务器」这节课中我会学到什么？

启动服务器，让客户端可以在本地连接。你通过在浏览器中直接运行的动手代码来练习 MCP Academy，全天候 AI 导师会在你学习这节课的过程中回答你的问题。

学习 MCP Academy 需要有经验吗？

无需任何先前经验。CoddyKit 上的 MCP Academy 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。这是第 3 节课，共 4 节。

「使用标准输入输出运行服务器」课时需要多长时间？

大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。

我能在这节 MCP Academy 课中编写并运行代码吗？

能。每节 MCP Academy 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。

此课程中的所有课时

← 返回 MCP Academy