深入解析Python中epoll开发服务端程序的代码实践
本文详细解读了Python中使用epoll开发服务端程序的源码，包括logging模块的使用、epoll的实现及处理‘读穿’的技巧。通过示例代码，学习者能掌握如何在服务端程序中高效地处理并发连接。
作为 Python 的初学者，学习别人的代码也是必要过程，本文主要是针对 《 Python中使用epoll开发服务端程序 》中的代码，进行源码注释说明。从代码中至少可以学习到如下三点：
- logging 模块的使用；
- epoll 的使用；
- 如何利用 try...catch 来处理“读穿”。
server端代码：
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#!/usr/bin/python
#-*- coding:utf-8 -*-
import
socket, logging
import
select, errno
logger
=
logging.getLogger(
"network-server"
)
def
InitLog():
logger.setLevel(logging.DEBUG)
fh
=
logging.FileHandler(
"network-server.log"
)
fh.setLevel(logging.DEBUG)
ch
=
logging.StreamHandler()
ch.setLevel(logging.ERROR)
formatter
=
logging.Formatter(
"%(asctime)s - %(name)s - %(levelname)s - %(message)s"
)
ch.setFormatter(formatter)
fh.setFormatter(formatter)
logger.addHandler(fh)
logger.addHandler(ch)
if
__name__
=
=
"__main__"
:
InitLog()
try
:
# 创建 TCP socket 作为监听 socket
listen_fd
=
socket.socket(socket.AF_INET, socket.SOCK_STREAM,
0
)
except
socket.error, msg:
logger.error(
"create socket failed"
)
try
:
# 设置 SO_REUSEADDR 选项
listen_fd.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR,
1
)
except
socket.error, msg:
logger.error(
"setsocketopt SO_REUSEADDR failed"
)
try
:
# 进行 bind -- 此处未指定 ip 地址，即 bind 了全部网卡 ip 上
listen_fd.bind(('',
2003
))
except
socket.error, msg:
logger.error(
"bind failed"
)
try
:
# 设置 listen 的 backlog 数
listen_fd.listen(
10
)
except
socket.error, msg:
logger.error(msg)
try
:
# 创建 epoll 句柄
epoll_fd
=
select.epoll()
# 向 epoll 句柄中注册 监听 socket 的 可读 事件
epoll_fd.register(listen_fd.fileno(), select.EPOLLIN)
except
select.error, msg:
logger.error(msg)
connections
=
{}
addresses
=
{}
datalist
=
{}
while
True
:
# epoll 进行 fd 扫描的地方 -- 未指定超时时间则为阻塞等待
epoll_list
=
epoll_fd.poll()
for
fd, events
in
epoll_list:
# 若为监听 fd 被激活
if
fd
=
=
listen_fd.fileno():
# 进行 accept -- 获得连接上来 client 的 ip 和 port，以及 socket 句柄
conn, addr
=
listen_fd.accept()
logger.debug(
"accept connection from %s, %d, fd = %d"
%
(addr[
0
], addr[
1
], conn.fileno()))
# 将连接 socket 设置为 非阻塞
conn.setblocking(
0
)
# 向 epoll 句柄中注册 连接 socket 的 可读 事件
epoll_fd.register(conn.fileno(), select.EPOLLIN | select.EPOLLET)
# 将 conn 和 addr 信息分别保存起来
connections[conn.fileno()]
=
conn
addresses[conn.fileno()]
=
addr
elif
select.EPOLLIN & events:
# 有 可读 事件激活
datas
=
''
while
True
:
try
:
# 从激活 fd 上 recv 10 字节数据
data
=
connections[fd].recv(
10
)
# 若当前没有接收到数据，并且之前的累计数据也没有
if
not
data
and
not
datas:
# 从 epoll 句柄中移除该 连接 fd
epoll_fd.unregister(fd)
# server 侧主动关闭该 连接 fd
connections[fd].close()
logger.debug(
"%s, %d closed"
%
(addresses[fd][
0
], addresses[fd][
1
]))
break
else
:
# 将接收到的数据拼接保存在 datas 中
datas
+
=
data
except
socket.error, msg:
# 在 非阻塞 socket 上进行 recv 需要处理 读穿 的情况
# 这里实际上是利用 读穿 出 异常 的方式跳到这里进行后续处理
if
msg.errno
=
=
errno.EAGAIN:
logger.debug(
"%s receive %s"
%
(fd, datas))
# 将已接收数据保存起来
datalist[fd]
=
datas
# 更新 epoll 句柄中连接d 注册事件为 可写
epoll_fd.modify(fd, select.EPOLLET | select.EPOLLOUT)
break
else
:
# 出错处理
epoll_fd.unregister(fd)
connections[fd].close()
logger.error(msg)
break
elif
select.EPOLLHUP & events:
# 有 HUP 事件激活
epoll_fd.unregister(fd)
connections[fd].close()
logger.debug(
"%s, %d closed"
%
(addresses[fd][
0
], addresses[fd][
1
]))
elif
select.EPOLLOUT & events:
# 有 可写 事件激活
sendLen
=
0
# 通过 while 循环确保将 buf 中的数据全部发送出去
while
True
:
# 将之前收到的数据发回 client -- 通过 sendLen 来控制发送位置
sendLen
+
=
connections[fd].send(datalist[fd][sendLen:])
# 在全部发送完毕后退出 while 循环
if
sendLen
=
=
len
(datalist[fd]):
break
# 更新 epoll 句柄中连接 fd 注册事件为 可读
epoll_fd.modify(fd, select.EPOLLIN | select.EPOLLET)
else
:
# 其他 epoll 事件不进行处理
continue
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import
socket
import
time
import
logging
logger
=
logging.getLogger(
"network-client"
)
logger.setLevel(logging.DEBUG)
fh
=
logging.FileHandler(
"network-client.log"
)
fh.setLevel(logging.DEBUG)
ch
=
logging.StreamHandler()
ch.setLevel(logging.ERROR)
formatter
=
logging.Formatter(
"%(asctime)s - %(name)s - %(levelname)s - %(message)s"
)
ch.setFormatter(formatter)
fh.setFormatter(formatter)
logger.addHandler(fh)
logger.addHandler(ch)
if
__name__
=
=
"__main__"
:
try
:
connFd
=
socket.socket(socket.AF_INET, socket.SOCK_STREAM,
0
)
except
socket.error, msg:
logger.error(msg)
try
:
connFd.connect((
"127.0.0.1"
,
2003
))
logger.debug(
"connect to network server success"
)
except
socket.error,msg:
logger.error(msg)
for
i
in
range
(
1
,
11
):
data
=
"The Number is %d"
%
i
if
connFd.send(data) !
=
len
(data):
logger.error(
"send data to network server failed"
)
break
readData
=
connFd.recv(
1024
)
print
readData
time.sleep(
1
)
connFd.close()
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client 命令行输出。
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[root@Betty Python]
# python epoll_client.py
The Number is 1
The Number is 2
The Number is 3
The Number is 4
The Number is 5
The Number is 6
The Number is 7
The Number is 8
The Number is 9
The Number is 10
[root@Betty Python]
#
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[root@Betty Python]
# vi network-client.log
2013-07-26 15:36:43,995 - network-client - DEBUG - connect to network server success
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[root@Betty Python]
# vi network-server.log
2013-07-26 15:36:43,995 - network-server - DEBUG - accept connection from 127.0.0.1, 34861, fd = 6
2013-07-26 15:36:43,995 - network-server - DEBUG - 6 receive The Number is 1
2013-07-26 15:36:44,996 - network-server - DEBUG - 6 receive The Number is 2
2013-07-26 15:36:45,996 - network-server - DEBUG - 6 receive The Number is 3
2013-07-26 15:36:46,996 - network-server - DEBUG - 6 receive The Number is 4
2013-07-26 15:36:47,996 - network-server - DEBUG - 6 receive The Number is 5
2013-07-26 15:36:48,997 - network-server - DEBUG - 6 receive The Number is 6
2013-07-26 15:36:49,998 - network-server - DEBUG - 6 receive The Number is 7
2013-07-26 15:36:50,999 - network-server - DEBUG - 6 receive The Number is 8
2013-07-26 15:36:52,000 - network-server - DEBUG - 6 receive The Number is 9
2013-07-26 15:36:53,001 - network-server - DEBUG - 6 receive The Number is 10
2013-07-26 15:36:54,002 - network-server - DEBUG - 127.0.0.1, 34861 closed
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