Linux Networking & TCP/IP for Developers · 课时

非阻塞套接字与 select()

使用非阻塞套接字和 select 模块，在单个 Python 进程中处理多个连接，实现可扩展的 I/O 多路复用。

非阻塞套接字与 select() 是 CoddyKit 上的免费 Linux Networking & TCP/IP for Developers 课时。这是第 4 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 Linux Networking & TCP/IP for Developers 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Linux Networking & TCP/IP for Developers 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。

The Blocking Problem

A simple recv() call blocks until data arrives. A single-threaded server can therefore only serve one client at a time.

To handle many clients without threads, we use non-blocking sockets combined with an I/O multiplexer like select().

Making a Socket Non-Blocking

Call setblocking(False) on a socket. Now recv() and send() return immediately, raising BlockingIOError if they would have blocked.

import socket
s = socket.socket()
s.setblocking(False)
print('blocking mode:', s.getblocking())

Introducing select()

select.select() watches lists of sockets and tells you which are ready.

It takes three lists: read, write, and error, and returns the subsets that are ready.

import select
readable, writable, errored = select.select(inputs, outputs, inputs)

The Server Setup

Create a listening socket, set it non-blocking, and add it to the inputs list. The listening socket becoming 'readable' means a new connection is waiting.

server = socket.socket()
server.setblocking(False)
server.bind(('localhost', 9000))
server.listen()
inputs = [server]

Accepting New Connections

When the listening socket is in the readable list, call accept(). Make the new client socket non-blocking and add it to inputs too.

if s is server:
    conn, addr = server.accept()
    conn.setblocking(False)
    inputs.append(conn)

Reading from Clients

For any other readable socket, call recv(). An empty bytes result means the client closed the connection, so remove it from inputs and close it.

data = s.recv(1024)
if data:
    print('got', data)
else:
    inputs.remove(s)
    s.close()

The Full Event Loop

Wrap accept and read logic in a while True loop driven by select(). This is the heart of an event-driven server.

while inputs:
    readable, _, _ = select.select(inputs, [], [])
    for s in readable:
        handle(s)

Handling Writes

For high-throughput servers you also track the writable list. Only send when the OS says the socket can accept data, avoiding partial-send stalls.

readable, writable, _ = select.select(inputs, outputs, [])
for s in writable:
    s.send(pending[s])

Beyond select: poll and epoll

select() is limited by the FD_SETSIZE constant and scans all sockets each call.

For thousands of connections, Linux offers select.poll() and the more scalable select.epoll(), which scale far better.

Where selectors Fits In

The high-level selectors module wraps the best available backend (epoll/kqueue) behind one API. Most production code uses it instead of raw select.

import selectors
sel = selectors.DefaultSelector()
sel.register(server, selectors.EVENT_READ)

Timeouts

Passing a timeout to select() lets the loop wake periodically even with no I/O, useful for housekeeping. A timeout of 0 polls without blocking.

readable, _, _ = select.select(inputs, [], [], 1.0)
if not readable:
    print('no activity this second')

Quick Check

Test your multiplexing knowledge.

Recap

You can now build a single-threaded multi-client server:

setblocking(False) for non-blocking sockets
select() to discover ready sockets
accept on the listening socket, recv on clients
Scale up with poll, epoll, or the selectors module

This builds on your TCP and UDP socket lessons toward scalable network services.

常见问题解答

「非阻塞套接字与 select()」课时是免费的吗？

是的 — 「非阻塞套接字与 select()」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 Linux Networking & TCP/IP for Developers 课程的其余内容，请升级到 CoddyKit PRO。 Linux Networking & TCP/IP for Developers 课程共包含 4 节课。

「非阻塞套接字与 select()」这节课中我会学到什么？

使用非阻塞套接字和 select 模块，在单个 Python 进程中处理多个连接，实现可扩展的 I/O 多路复用。你通过在浏览器中直接运行的动手代码来练习 Linux Networking & TCP/IP for Developers，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 Linux Networking & TCP/IP for Developers 需要有经验吗？

无需任何先前经验。CoddyKit 上的 Linux Networking & TCP/IP for Developers 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 4 节课，共 4 节。

「非阻塞套接字与 select()」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 Linux Networking & TCP/IP for Developers 课中编写并运行代码吗？

能。每节 Linux Networking & TCP/IP for Developers 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 Linux Networking & TCP/IP for Developers