来源：http://www.haiyun.me/archives/1056.html
有许多封装好的异步非阻塞IO多路复用框架，底层在linux基于最新的epoll实现，为了更好的使用，了解其底层原理还是有必要的。
下面记录下分别基于Select/Poll/Epoll的echo server实现。
Python Select Server，可监控事件数量有限制：
#!/usr/bin/python
# -*- coding: utf-8 -*-
import select
import socket</span>
import Queue
server = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
server.setblocking(False)
server.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR , 1)
server_address= ('192.168.1.5',8080)
server.bind(server_address)
server.listen(10)
#select轮询等待读socket集合
inputs = [server]
#select轮询等待写socket集合
outputs = []
message_queues = {}
#select超时时间
timeout = 20
while True:
print "等待活动连接......"
readable , writable , exceptional = select.select(inputs, outputs, inputs, timeout)
if not (readable or writable or exceptional) :
print "select超时无活动连接，重新select...... "
continue;
#循环可读事件
for s in readable :
#如果是server监听的socket
if s is server:
#同意连接
connection, client_address = s.accept()
print "新连接： ", client_address
connection.setblocking(0)
#将连接加入到select可读事件队列
inputs.append(connection)
#新建连接为key的字典，写回读取到的消息
message_queues[connection] = Queue.Queue()
else:
#不是本机监听就是客户端发来的消息
data = s.recv(1024)
if data :
print "收到数据：" , data , "客户端：",s.getpeername()
message_queues[s].put(data)
if s not in outputs:
#将读取到的socket加入到可写事件队列
outputs.append(s)
else:
#空白消息，关闭连接
print "关闭连接：", client_address
if s in outputs :
outputs.remove(s)
inputs.remove(s)
s.close()
del message_queues[s]
for s in writable:
try:
msg = message_queues[s].get_nowait()
except Queue.Empty:
print "连接：" , s.getpeername() , '消息队列为空'
outputs.remove(s)
else:
print "发送数据：" , msg , "到", s.getpeername()
s.send(msg)
for s in exceptional:
print "异常连接：", s.getpeername()
inputs.remove(s)
if s in outputs:
outputs.remove(s)
s.close()
del message_queues[s]
Python Poll Server，Select升级版，无可监控事件数量限制，还是要轮询所有事件：
#!/usr/bin/python
# -*- coding: utf-8 -*-
import socket
import select
import Queue
server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server.setblocking(False)
server.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
server_address = ("192.168.1.5", 8080)
server.bind(server_address)
server.listen(5)
print "服务器启动成功，监听IP：" , server_address
message_queues = {}
#超时，毫秒
timeout = 5000
#监听哪些事件
READ_ONLY = ( select.POLLIN | select.POLLPRI | select.POLLHUP | select.POLLERR)
READ_WRITE = (READ_ONLY|select.POLLOUT)
#新建轮询事件对象
poller = select.poll()
#注册本机监听socket到等待可读事件事件集合
poller.register(server,READ_ONLY)
#文件描述符到socket映射
fd_to_socket = {server.fileno():server,}
while True:
print "等待活动连接......"
#轮询注册的事件集合
events = poller.poll(timeout)
if not events:
print "poll超时，无活动连接，重新poll......"
continue
print "有" , len(events), "个新事件，开始处理......"
for fd ,flag in events:
s = fd_to_socket[fd]
#可读事件
if flag & (select.POLLIN | select.POLLPRI) :
if s is server :
#如果socket是监听的server代表有新连接
connection , client_address = s.accept()
print "新连接：" , client_address
connection.setblocking(False)
fd_to_socket[connection.fileno()] = connection
#加入到等待读事件集合
poller.register(connection,READ_ONLY)
message_queues[connection] = Queue.Queue()
else :
#接收客户端发送的数据
data = s.recv(1024)
if data:
print "收到数据：" , data , "客户端：" , s.getpeername()
message_queues[s].put(data)
#修改读取到消息的连接到等待写事件集合
poller.modify(s,READ_WRITE)
else :
# Close the connection
print " closing" , s.getpeername()
# Stop listening for input on the connection
poller.unregister(s)
s.close()
del message_queues[s]
#连接关闭事件
elif flag & select.POLLHUP :
print " Closing ", s.getpeername() ,"(HUP)"
poller.unregister(s)
s.close()
#可写事件
elif flag & select.POLLOUT :
try:
msg = message_queues[s].get_nowait()
except Queue.Empty:
print s.getpeername() , " queue empty"
poller.modify(s,READ_ONLY)
else :
print "发送数据：" , data , "客户端：" , s.getpeername()
s.send(msg)
#异常事件
elif flag & select.POLLERR:
print " exception on" , s.getpeername()
poller.unregister(s)
s.close()
del message_queues[s]</span>Python Epoll Server，基于回调的事件通知模式，轻松管理大量连接：
#!/usr/bin/python
# -*- coding: utf-8 -*-
import socket, select
import Queue
serversocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
serversocket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
server_address = ("192.168.1.5", 8080)
serversocket.bind(server_address)
serversocket.listen(1)
print "服务器启动成功，监听IP：" , server_address
serversocket.setblocking(0)
timeout = 10
#新建epoll事件对象，后续要监控的事件添加到其中
epoll = select.epoll()
#添加服务器监听fd到等待读事件集合
epoll.register(serversocket.fileno(), select.EPOLLIN)
message_queues = {}
fd_to_socket = {serversocket.fileno():serversocket,}
while True:
print "等待活动连接......"
#轮询注册的事件集合
events = epoll.poll(timeout)
if not events:
print "epoll超时无活动连接，重新轮询......"
continue
print "有" , len(events), "个新事件，开始处理......"
for fd, event in events:
socket = fd_to_socket[fd]
#可读事件
if event & select.EPOLLIN:
#如果活动socket为服务器所监听，有新连接
if socket == serversocket:
connection, address = serversocket.accept()
print "新连接：" , address
connection.setblocking(0)
#注册新连接fd到待读事件集合
epoll.register(connection.fileno(), select.EPOLLIN)
fd_to_socket[connection.fileno()] = connection
message_queues[connection] = Queue.Queue()
#否则为客户端发送的数据
else:
data = socket.recv(1024)
if data:
print "收到数据：" , data , "客户端：" , socket.getpeername()
message_queues[socket].put(data)
#修改读取到消息的连接到等待写事件集合
epoll.modify(fd, select.EPOLLOUT)
#可写事件
elif event & select.EPOLLOUT:
try:
msg = message_queues[socket].get_nowait()
except Queue.Empty:
print socket.getpeername() , " queue empty"
epoll.modify(fd, select.EPOLLIN)
else :
print "发送数据：" , data , "客户端：" , socket.getpeername()
socket.send(msg)
#关闭事件
elif event & select.EPOLLHUP:
epoll.unregister(fd)
fd_to_socket[fd].close()
del fd_to_socket[fd]
epoll.unregister(serversocket.fileno())
epoll.close()
serversocket.close()
