关于程序员:python之socket编程

本章内容

1、socket

2、IO 多路复用

3、socketserver

Socket

socket 起源于 Unix，而 Unix/Linux 根本哲学之一就是“所有皆文件”，对于文件用【关上】【读写】【敞开】模式来操作。socket 就是该模式的一个实现，socket 即是一种非凡的文件，一些 socket 函数就是对其进行的操作（读 / 写 IO、关上、敞开）

基本上，Socket 是任何一种计算机网络通信中最根底的内容。例如当你在浏览器地址栏中输出 http://www.cnblogs.com/ 时，你会关上一个套接字，而后连贯到 http://www.cnblogs.com/ 并读取响应的页面而后而后显示进去。而其余一些聊天客户端如 gtalk 和 skype 也是相似。任何网络通讯都是通过 Socket 来实现的。

Python 官网对于 Socket 的函数请看 http://docs.python.org/library/socket.html

socket 和 file 的区别：

1、file 模块是针对某个指定文件进行【关上】【读写】【敞开】

2、socket 模块是针对 服务器端 和 客户端 Socket 进行【关上】【读写】【敞开】

那咱们就先来创立一个 socket 服务端吧

import socket

sk = socket.socket()
sk.bind(("127.0.0.1",8080))
sk.listen(5)

conn,address = sk.accept()
sk.sendall(bytes("Hello world",encoding="utf-8"))

server

import socket

obj = socket.socket()
obj.connect(("127.0.0.1",8080))

ret = str(obj.recv(1024),encoding="utf-8")
print(ret)

View Code

socket 更多功能

    def bind(self, address): # real signature unknown; restored from __doc__
        """
        bind(address)
        
        Bind the socket to a local address.  For IP sockets, the address is a
        pair (host, port); the host must refer to the local host. For raw packet
        sockets the address is a tuple (ifname, proto [,pkttype [,hatype]])
        """''' 将套接字绑定到本地地址。是一个 IP 套接字的地址对(主机、端口), 主机必须参考本地主机。'''
        pass

    def close(self): # real signature unknown; restored from __doc__
        """
        close()
        
        Close the socket.  It cannot be used after this call.
        """''' 敞开 socket'''
        pass

    def connect(self, address): # real signature unknown; restored from __doc__
        """
        connect(address)
        
        Connect the socket to a remote address.  For IP sockets, the address
        is a pair (host, port).
        """''' 将套接字连贯到近程地址。IP 套接字的地址 '''
        pass

    def connect_ex(self, address): # real signature unknown; restored from __doc__
        """
        connect_ex(address) -> errno
        
        This is like connect(address), but returns an error code (the errno value)
        instead of raising an exception when an error occurs.
        """
        pass

    def detach(self): # real signature unknown; restored from __doc__
        """
        detach()
        
        Close the socket object without closing the underlying file descriptor.
        The object cannot be used after this call, but the file descriptor
        can be reused for other purposes.  The file descriptor is returned.
        """''' 敞开套接字对象没有敞开底层的文件描述符。'''
        pass

    def fileno(self): # real signature unknown; restored from __doc__
        """
        fileno() -> integer
        
        Return the integer file descriptor of the socket.
        """''' 返回整数的套接字的文件描述符。'''
        return 0

    def getpeername(self): # real signature unknown; restored from __doc__
        """
        getpeername() -> address info
        
        Return the address of the remote endpoint.  For IP sockets, the address
        info is a pair (hostaddr, port).
            """''' 返回近程端点的地址。IP 套接字的地址 '''
        pass

    def getsockname(self): # real signature unknown; restored from __doc__
        """
        getsockname() -> address info
        
        Return the address of the local endpoint.  For IP sockets, the address
        info is a pair (hostaddr, port).
        """''' 返回近程端点的地址。IP 套接字的地址 '''
        pass

    def getsockopt(self, level, option, buffersize=None): # real signature unknown; restored from __doc__
        """
        getsockopt(level, option[, buffersize]) -> value
        
        Get a socket option.  See the Unix manual for level and option.
        If a nonzero buffersize argument is given, the return value is a
        string of that length; otherwise it is an integer.
        """''' 失去一个套接字选项 '''
        pass

    def gettimeout(self): # real signature unknown; restored from __doc__
        """
        gettimeout() -> timeout
        
        Returns the timeout in seconds (float) associated with socket 
        operations. A timeout of None indicates that timeouts on socket 
        operations are disabled.
        """''' 返回的超时秒数 (浮动) 与套接字相关联 '''
        return timeout

    def ioctl(self, cmd, option): # real signature unknown; restored from __doc__
        """
        ioctl(cmd, option) -> long
        
        Control the socket with WSAIoctl syscall. Currently supported 'cmd' values are
        SIO_RCVALL:  'option' must be one of the socket.RCVALL_* constants.
        SIO_KEEPALIVE_VALS:  'option' is a tuple of (onoff, timeout, interval).
        """
        return 0

    def listen(self, backlog=None): # real signature unknown; restored from __doc__
        """
        listen([backlog])
        
        Enable a server to accept connections.  If backlog is specified, it must be
        at least 0 (if it is lower, it is set to 0); it specifies the number of
        unaccepted connections that the system will allow before refusing new
        connections. If not specified, a default reasonable value is chosen.
        """''' 使服务器可能承受连贯。'''
        pass

    def recv(self, buffersize, flags=None): # real signature unknown; restored from __doc__
        """
        recv(buffersize[, flags]) -> data
        
        Receive up to buffersize bytes from the socket.  For the optional flags
        argument, see the Unix manual.  When no data is available, block until
        at least one byte is available or until the remote end is closed.  When
        the remote end is closed and all data is read, return the empty string.
        """''' 当没有数据可用, 阻塞, 直到至多一个字节是可用的或近程完结之前敞开。'''
        pass

    def recvfrom(self, buffersize, flags=None): # real signature unknown; restored from __doc__
        """
        recvfrom(buffersize[, flags]) -> (data, address info)
        
        Like recv(buffersize, flags) but also return the sender's address info."""
        pass

    def recvfrom_into(self, buffer, nbytes=None, flags=None): # real signature unknown; restored from __doc__
        """
        recvfrom_into(buffer[, nbytes[, flags]]) -> (nbytes, address info)
        
        Like recv_into(buffer[, nbytes[, flags]]) but also return the sender's address info."""
        pass

    def recv_into(self, buffer, nbytes=None, flags=None): # real signature unknown; restored from __doc__
        """
        recv_into(buffer, [nbytes[, flags]]) -> nbytes_read
        
        A version of recv() that stores its data into a buffer rather than creating 
        a new string.  Receive up to buffersize bytes from the socket.  If buffersize 
        is not specified (or 0), receive up to the size available in the given buffer.
        
        See recv() for documentation about the flags.
        """
        pass

    def send(self, data, flags=None): # real signature unknown; restored from __doc__
        """
        send(data[, flags]) -> count
        
        Send a data string to the socket.  For the optional flags
        argument, see the Unix manual.  Return the number of bytes
        sent; this may be less than len(data) if the network is busy.
        """''' 发送一个数据字符串到套接字。'''
        pass

    def sendall(self, data, flags=None): # real signature unknown; restored from __doc__
        """
        sendall(data[, flags])
        
        Send a data string to the socket.  For the optional flags
        argument, see the Unix manual.  This calls send() repeatedly
        until all data is sent.  If an error occurs, it's impossible
        to tell how much data has been sent.
        """''' 发送一个数据字符串到套接字，直到所有数据发送实现 '''
        pass

    def sendto(self, data, flags=None, *args, **kwargs): # real signature unknown; NOTE: unreliably restored from __doc__ 
        """
        sendto(data[, flags], address) -> count
        
        Like send(data, flags) but allows specifying the destination address.
        For IP sockets, the address is a pair (hostaddr, port).
        """
        pass

    def setblocking(self, flag): # real signature unknown; restored from __doc__
        """
        setblocking(flag)
        
        Set the socket to blocking (flag is true) or non-blocking (false).
        setblocking(True) is equivalent to settimeout(None);
        setblocking(False) is equivalent to settimeout(0.0).
        """''' 是否阻塞（默认 True），如果设置 False，那么 accept 和 recv 时一旦无数据，则报错。'''
        pass

    def setsockopt(self, level, option, value): # real signature unknown; restored from __doc__
        """
        setsockopt(level, option, value)
        
        Set a socket option.  See the Unix manual for level and option.
        The value argument can either be an integer or a string.
        """
        pass

    def settimeout(self, timeout): # real signature unknown; restored from __doc__
        """
        settimeout(timeout)
        
        Set a timeout on socket operations.  'timeout' can be a float,
        giving in seconds, or None.  Setting a timeout of None disables
        the timeout feature and is equivalent to setblocking(1).
        Setting a timeout of zero is the same as setblocking(0).
        """
        pass

    def share(self, process_id): # real signature unknown; restored from __doc__
        """
        share(process_id) -> bytes
        
        Share the socket with another process.  The target process id
        must be provided and the resulting bytes object passed to the target
        process.  There the shared socket can be instantiated by calling
        socket.fromshare().
        """return b""

    def shutdown(self, flag): # real signature unknown; restored from __doc__
        """
        shutdown(flag)
        
        Shut down the reading side of the socket (flag == SHUT_RD), the writing side
        of the socket (flag == SHUT_WR), or both ends (flag == SHUT_RDWR).
        """
        pass

    def _accept(self): # real signature unknown; restored from __doc__
        """
        _accept() -> (integer, address info)
        
        Wait for an incoming connection.  Return a new socket file descriptor
        representing the connection, and the address of the client.
        For IP sockets, the address info is a pair (hostaddr, port).
        """
        pass
    

更多功能

注：撸主晓得大家懒，所以把全副性能的中文标记在每个性能的上面啦。上面撸主列一些常常用到的吧

sk.bind(address)

s.bind(address) 将套接字绑定到地址。address 地址的格局取决于地址族。在 AF\_INET 下，以元组（host,port）的模式示意地址。

sk.listen(backlog)

开始监听传入连贯。backlog 指定在回绝连贯之前，能够挂起的最大连贯数量。

      backlog 等于 5，示意内核曾经接到了连贯申请，但服务器还没有调用 accept 进行解决的连贯个数最大为 5
      这个值不能无限大，因为要在内核中保护连贯队列

sk.setblocking(bool)

是否阻塞（默认 True），如果设置 False，那么 accept 和 recv 时一旦无数据，则报错。

sk.accept()

承受连贯并返回（conn,address）, 其中 conn 是新的套接字对象，能够用来接管和发送数据。address 是连贯客户端的地址。

接管 TCP 客户的连贯（阻塞式）期待连贯的到来

sk.connect(address)

连贯到 address 处的套接字。个别，address 的格局为元组（hostname,port）, 如果连贯出错，返回 socket.error 谬误。

sk.connect\_ex(address)

同上，只不过会有返回值，连贯胜利时返回 0，连贯失败时候返回编码，例如：10061

sk.close()

敞开套接字

sk.recv(bufsize[,flag])

承受套接字的数据。数据以字符串模式返回，bufsize 指定 最多 能够接管的数量。flag 提供无关音讯的其余信息，通常能够疏忽。

sk.recvfrom(bufsize[.flag])

与 recv()相似，但返回值是（data,address）。其中 data 是蕴含接收数据的字符串，address 是发送数据的套接字地址。

sk.send(string[,flag])

将 string 中的数据发送到连贯的套接字。返回值是要发送的字节数量，该数量可能小于 string 的字节大小。即：可能未将指定内容全副发送。

sk.sendall(string[,flag])

将 string 中的数据发送到连贯的套接字，但在返回之前会尝试发送所有数据。胜利返回 None，失败则抛出异样。

      外部通过递归调用 send，将所有内容发送进来。

sk.sendto(string[,flag],address)

将数据发送到套接字，address 是模式为（ipaddr，port）的元组，指定近程地址。返回值是发送的字节数。该函数次要用于 UDP 协定。

sk.settimeout(timeout)

设置套接字操作的超期间，timeout 是一个浮点数，单位是秒。值为 None 示意没有超期间。个别，超期间应该在刚创立套接字时设置，因为它们可能用于连贯的操作（如 client 连贯最多期待 5s）

sk.getpeername()

返回连贯套接字的近程地址。返回值通常是元组（ipaddr,port）。

sk.getsockname()

返回套接字本人的地址。通常是一个元组(ipaddr,port)

sk.fileno()

套接字的文件描述符

TCP：

import  socketserver
服务端

class Myserver(socketserver.BaseRequestHandler):

    def handle(self):

        conn = self.request
        conn.sendall(bytes("你好，我是机器人",encoding="utf-8"))
        while True:
            ret_bytes = conn.recv(1024)
            ret_str = str(ret_bytes,encoding="utf-8")
            if ret_str == "q":
                break
            conn.sendall(bytes(ret_str+"你好我好大家好",encoding="utf-8"))

if __name__ == "__main__":
    server = socketserver.ThreadingTCPServer(("127.0.0.1",8080),Myserver)
    server.serve_forever()

客户端

import socket

obj = socket.socket()

obj.connect(("127.0.0.1",8080))

ret_bytes = obj.recv(1024)
ret_str = str(ret_bytes,encoding="utf-8")
print(ret_str)

while True:
    inp = input("你好请问您有什么问题？\n >>>")
    if inp == "q":
        obj.sendall(bytes(inp,encoding="utf-8"))
        break
    else:
        obj.sendall(bytes(inp, encoding="utf-8"))
        ret_bytes = obj.recv(1024)
        ret_str = str(ret_bytes,encoding="utf-8")
        print(ret_str)

案例一 机器人聊天

服务端

import socket

sk = socket.socket()

sk.bind(("127.0.0.1",8080))
sk.listen(5)

while True:
    conn,address = sk.accept()
    conn.sendall(bytes("欢迎光临我爱我家",encoding="utf-8"))

    size = conn.recv(1024)
    size_str = str(size,encoding="utf-8")
    file_size = int(size_str)

    conn.sendall(bytes("开始传送", encoding="utf-8"))

    has_size = 0
    f = open("db_new.jpg","wb")
    while True:
        if file_size == has_size:
            break
        date = conn.recv(1024)
        f.write(date)
        has_size += len(date)

    f.close()

客户端

import socket
import os

obj = socket.socket()

obj.connect(("127.0.0.1",8080))

ret_bytes = obj.recv(1024)
ret_str = str(ret_bytes,encoding="utf-8")
print(ret_str)

size = os.stat("yan.jpg").st_size
obj.sendall(bytes(str(size),encoding="utf-8"))

obj.recv(1024)

with open("yan.jpg","rb") as f:
    for line in f:
        obj.sendall(line)

案例二 上传文件

UdP

import socket
ip_port = ('127.0.0.1',9999)
sk = socket.socket(socket.AF_INET,socket.SOCK_DGRAM,0)
sk.bind(ip_port)

while True:
    data = sk.recv(1024)
    print data




import socket
ip_port = ('127.0.0.1',9999)

sk = socket.socket(socket.AF_INET,socket.SOCK_DGRAM,0)
while True:
    inp = input('数据：').strip()
    if inp == 'exit':
        break
    sk.sendto(bytes(inp,encoding = "utf-8"),ip_port)

sk.close()

udp 传输

WEB 服务利用：

## IO 多路复用 

I/O（input/output），即输出 / 输入端口。每个设施都会有一个专用的 I / O 地址，用来解决本人的输入输出信息 首先什么是 I /O：

I/ O 分为磁盘 io 和网络 io，这里说的是网络 io

IO 多路复用:

I/ O 多路复用指：通过一种机制，能够监督多个描述符(socket)，一旦某个描述符就绪（个别是读就绪或者写就绪），可能告诉程序进行相应的读写操作。

Linux

Linux 中的 select，poll，epoll 都是 IO 多路复用的机制。

Linux 下网络 I / O 应用 socket 套接字来通信，一般 I / O 模型只能监听一个 socket，而 I / O 多路复用可同时监听多个 socket.

I/ O 多路复用防止阻塞在 io 上，本来为多过程或多线程来接管多个连贯的音讯变为单过程或单线程保留多个 socket 的状态后轮询解决.

Python  

Python 中有一个 select 模块，其中提供了：select、poll、epoll 三个办法，别离调用零碎的 select，poll，epoll 从而实现 IO 多路复用。

对于 select 模块操作的办法：

`
import socket
import select

sk1 = socket.socket()
sk1.bind((“127.0.0.1”,8001))
sk1.listen()

sk2 = socket.socket()
sk2.bind((“127.0.0.1”,8002))
sk2.listen()

sk3 = socket.socket()
sk3.bind((“127.0.0.1”,8003))
sk3.listen()

li = [sk1,sk2,sk3]

while True:
r_list,w_list,e_list = select.select(li,[],[],1) # r_list 可变动的
for line in r_list:
conn,address = line.accept()
conn.sendall(bytes(“Hello World !”,encoding=”utf-8″))
`

利用 select 监听终端操作实例

`
服务端：
sk1 = socket.socket()
sk1.bind((“127.0.0.1″,8001))
sk1.listen()

inpu = [sk1,]

while True:
r_list,w_list,e_list = select.select(inpu,[],[],1)
for sk in r_list:
if sk == sk1:
conn,address = sk.accept()
inpu.append(conn)
else:
try:
ret = str(sk.recv(1024),encoding=”utf-8″)
sk.sendall(bytes(ret+”hao”,encoding=”utf-8″))
except Exception as ex:
inpu.remove(sk)

客户端
import socket

obj = socket.socket()

obj.connect((‘127.0.0.1’,8001))

while True:
inp = input(“Please(q\ 退出):\n>>>”)
obj.sendall(bytes(inp,encoding=”utf-8″))
if inp == “q”:
break
ret = str(obj.recv(1024),encoding=”utf-8″)
print(ret)
`

利用 select 实现伪同时解决多个 Socket 客户端申请

`
服务端：
import socket
sk1 = socket.socket()
sk1.bind((“127.0.0.1”,8001))
sk1.listen()
inputs = [sk1]
import select
message_dic = {}
outputs = []
while True:

r_list, w_list, e_list = select.select(inputs,[],inputs,1)
print(“ 正在监听的 socket 对象 %d” % len(inputs))
print(r_list)
for sk1_or_conn in r_list:
if sk1_or_conn == sk1:
conn,address = sk1_or_conn.accept()
inputs.append(conn)
message_dic[conn] = []
else:
try:
data_bytes = sk1_or_conn.recv(1024)
data_str = str(data_bytes,encoding=”utf-8″)
sk1_or_conn.sendall(bytes(data_str+” 好 ”,encoding=”utf-8″))
except Exception as ex:
inputs.remove(sk1_or_conn)
else:
data_str = str(data_bytes,encoding=”utf-8″)
message_dic[sk1_or_conn].append(data_str)
outputs.append(sk1_or_conn)
for conn in w_list:
recv_str = message_dicconn
del message_dicconn
conn.sendall(bytes(recv_str+” 好 ”,encoding=”utf-8″))
for sk in e_list:
inputs.remove(sk)

客户端：
import socket

obj = socket.socket()

obj.connect((‘127.0.0.1’,8001))

while True:
inp = input(“Please(q\ 退出):\n>>>”)
obj.sendall(bytes(inp,encoding=”utf-8″))
if inp == “q”:
break
ret = str(obj.recv(1024),encoding=”utf-8″)
print(ret)
`

利用 select 实现伪同时解决多个 Socket 客户端申请读写拆散

## socketserver

SocketServer 外部应用 IO 多路复用 以及“多线程”和“多过程”，从而实现并发解决多个客户端申请的 Socket 服务端。即：每个客户端申请连贯到服务器时，Socket 服务端都会在服务器是创立一个“线程”或者“过程”专门负责解决以后客户端的所有申请。

ThreadingTCPServer

ThreadingTCPServer 实现的 Soket 服务器外部会为每个 client 创立一个“线程”，该线程用来和客户端进行交互。

1、ThreadingTCPServer 根底

应用 ThreadingTCPServer:

– 创立一个继承自 SocketServer.BaseRequestHandler 的类
– 类中必须定义一个名称为 handle 的办法
– 启动 ThreadingTCPServer

`
import socketserver

class Myserver(socketserver.BaseRequestHandler):

def handle(self):

conn = self.request
conn.sendall(bytes(“ 你好，我是机器人 ”,encoding=”utf-8″))
while True:
ret_bytes = conn.recv(1024)
ret_str = str(ret_bytes,encoding=”utf-8″)
if ret_str == “q”:
break
conn.sendall(bytes(ret_str+” 你好我好大家好 ”,encoding=”utf-8″))

if name == “__main__”:
server = socketserver.ThreadingTCPServer((“127.0.0.1”,8080),Myserver)
server.serve_forever()
`

服务端

`
import socket

obj = socket.socket()

obj.connect((“127.0.0.1″,8080))

ret_bytes = obj.recv(1024)
ret_str = str(ret_bytes,encoding=”utf-8”)
print(ret_str)

while True:
inp = input(“ 你好请问您有什么问题？\n >>>”)
if inp == “q”:
obj.sendall(bytes(inp,encoding=”utf-8″))
break
else:
obj.sendall(bytes(inp, encoding=”utf-8″))
ret_bytes = obj.recv(1024)
ret_str = str(ret_bytes,encoding=”utf-8″)
print(ret_str)
`

客户端

2、ThreadingTCPServer 源码分析

ThreadingTCPServer 的类图关系如下：

外部调用流程为：

– 启动服务端程序
– 执行 TCPServer.\_\_init\_\_ 办法，创立服务端 Socket 对象并绑定 IP 和 端口
– 执行 BaseServer.\_\_init\_\_ 办法，将自定义的继承自 SocketServer.BaseRequestHandler 的类 MyRequestHandle 赋值给 self.RequestHandlerClass
– 执行 BaseServer.server\_forever 办法，While 循环始终监听是否有客户端申请达到 …
– 当客户端连贯达到服务器
– 执行 ThreadingMixIn.process\_request 办法，创立一个“线程”用来解决申请
– 执行 ThreadingMixIn.process\_request\_thread 办法
– 执行 BaseServer.finish\_request 办法，执行 self.RequestHandlerClass()  即：执行 自定义 MyRequestHandler 的构造方法（主动调用基类 BaseRequestHandler 的构造方法，在该构造方法中又会调用 MyRequestHandler 的 handle 办法）

绝对应的源码如下：

`
class BaseServer:

“””Base class for server classes.

Methods for the caller:

– __init__(server_address, RequestHandlerClass)
– serve_forever(poll_interval=0.5)
– shutdown()
– handle_request() # if you do not use serve_forever()
– fileno() -> int # for select()

Methods that may be overridden:

– server_bind()
– server_activate()
– get_request() -> request, client_address
– handle_timeout()
– verify_request(request, client_address)
– server_close()
– process_request(request, client_address)
– shutdown_request(request)
– close_request(request)
– handle_error()

Methods for derived classes:

– finish_request(request, client_address)

Class variables that may be overridden by derived classes or
instances:

– timeout
– address_family
– socket_type
– allow_reuse_address

Instance variables:

– RequestHandlerClass
– socket

“””

timeout = None

def __init__(self, server_address, RequestHandlerClass):
“””Constructor. May be extended, do not override.”””
self.server_address = server_address
self.RequestHandlerClass = RequestHandlerClass
self.__is_shut_down = threading.Event()
self.__shutdown_request = False

def server_activate(self):
“””Called by constructor to activate the server.

May be overridden.

“””
pass

def serve_forever(self, poll_interval=0.5):
“””Handle one request at a time until shutdown.

Polls for shutdown every poll_interval seconds. Ignores
self.timeout. If you need to do periodic tasks, do them in
another thread.
“””
self.__is_shut_down.clear()
try:
while not self.__shutdown_request:
# XXX: Consider using another file descriptor or
# connecting to the socket to wake this up instead of
# polling. Polling reduces our responsiveness to a
# shutdown request and wastes cpu at all other times.
r, w, e = _eintr_retry(select.select, [self], [], [],
poll_interval)
if self in r:
self._handle_request_noblock()
finally:
self.__shutdown_request = False
self.__is_shut_down.set()

def shutdown(self):
“””Stops the serve_forever loop.

Blocks until the loop has finished. This must be called while
serve_forever() is running in another thread, or it will
deadlock.
“””
self.__shutdown_request = True
self.__is_shut_down.wait()

# The distinction between handling, getting, processing and
# finishing a request is fairly arbitrary. Remember:
#
# – handle_request() is the top-level call. It calls
# select, get_request(), verify_request() and process_request()
# – get_request() is different for stream or datagram sockets
# – process_request() is the place that may fork a new process
# or create a new thread to finish the request
# – finish_request() instantiates the request handler class;
# this constructor will handle the request all by itself

def handle_request(self):
“””Handle one request, possibly blocking.

Respects self.timeout.
“””
# Support people who used socket.settimeout() to escape
# handle_request before self.timeout was available.
timeout = self.socket.gettimeout()
if timeout is None:
timeout = self.timeout
elif self.timeout is not None:
timeout = min(timeout, self.timeout)
fd_sets = _eintr_retry(select.select, [self], [], [], timeout)
if not fd_sets[0]:
self.handle_timeout()
return
self._handle_request_noblock()

def _handle_request_noblock(self):
“””Handle one request, without blocking.

I assume that select.select has returned that the socket is
readable before this function was called, so there should be
no risk of blocking in get_request().
“””
try:
request, client_address = self.get_request()
except socket.error:
return
if self.verify_request(request, client_address):
try:
self.process_request(request, client_address)
except:
self.handle_error(request, client_address)
self.shutdown_request(request)

def handle_timeout(self):
“””Called if no new request arrives within self.timeout.

Overridden by ForkingMixIn.
“””
pass

def verify_request(self, request, client_address):
“””Verify the request. May be overridden.

Return True if we should proceed with this request.

“””
return True

def process_request(self, request, client_address):
“””Call finish_request.

Overridden by ForkingMixIn and ThreadingMixIn.

“””
self.finish_request(request, client_address)
self.shutdown_request(request)

def server_close(self):
“””Called to clean-up the server.

May be overridden.

“””
pass

def finish_request(self, request, client_address):
“””Finish one request by instantiating RequestHandlerClass.”””
self.RequestHandlerClass(request, client_address, self)

def shutdown_request(self, request):
“””Called to shutdown and close an individual request.”””
self.close_request(request)

def close_request(self, request):
“””Called to clean up an individual request.”””
pass

def handle_error(self, request, client_address):
“””Handle an error gracefully. May be overridden.

The default is to print a traceback and continue.

“””
print ‘-‘*40
print ‘Exception happened during processing of request from’,
print client_address
import traceback
traceback.print_exc() # XXX But this goes to stderr!
print ‘-‘*40
`

Baseserver

`
class TCPServer(BaseServer):

“””Base class for various socket-based server classes.

Defaults to synchronous IP stream (i.e., TCP).

Methods for the caller:

– __init__(server_address, RequestHandlerClass, bind_and_activate=True)
– serve_forever(poll_interval=0.5)
– shutdown()
– handle_request() # if you don’t use serve_forever()
– fileno() -> int # for select()

Methods that may be overridden:

– server_bind()
– server_activate()
– get_request() -> request, client_address
– handle_timeout()
– verify_request(request, client_address)
– process_request(request, client_address)
– shutdown_request(request)
– close_request(request)
– handle_error()

Methods for derived classes:

– finish_request(request, client_address)

Class variables that may be overridden by derived classes or
instances:

– timeout
– address_family
– socket_type
– request_queue_size (only for stream sockets)
– allow_reuse_address

Instance variables:

– server_address
– RequestHandlerClass
– socket

“””

address_family = socket.AF_INET

socket_type = socket.SOCK_STREAM

request_queue_size = 5

allow_reuse_address = False

def __init__(self, server_address, RequestHandlerClass, bind_and_activate=True):
“””Constructor. May be extended, do not override.”””
BaseServer.__init__(self, server_address, RequestHandlerClass)
self.socket = socket.socket(self.address_family,
self.socket_type)
if bind_and_activate:
try:
self.server_bind()
self.server_activate()
except:
self.server_close()
raise

def server_bind(self):
“””Called by constructor to bind the socket.

May be overridden.

“””
if self.allow_reuse_address:
self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
self.socket.bind(self.server_address)
self.server_address = self.socket.getsockname()

def server_activate(self):
“””Called by constructor to activate the server.

May be overridden.

“””
self.socket.listen(self.request_queue_size)

def server_close(self):
“””Called to clean-up the server.

May be overridden.

“””
self.socket.close()

def fileno(self):
“””Return socket file number.

Interface required by select().

“””
return self.socket.fileno()

def get_request(self):
“””Get the request and client address from the socket.

May be overridden.

“””
return self.socket.accept()

def shutdown_request(self, request):
“””Called to shutdown and close an individual request.”””
try:
#explicitly shutdown. socket.close() merely releases
#the socket and waits for GC to perform the actual close.
request.shutdown(socket.SHUT_WR)
except socket.error:
pass #some platforms may raise ENOTCONN here
self.close_request(request)

def close_request(self, request):
“””Called to clean up an individual request.”””
request.close()
`

TCP server

`
class ThreadingMixIn:
“””Mix-in class to handle each request in a new thread.”””

# Decides how threads will act upon termination of the
# main process
daemon_threads = False

def process_request_thread(self, request, client_address):
“””Same as in BaseServer but as a thread.

In addition, exception handling is done here.

“””
try:
self.finish_request(request, client_address)
self.shutdown_request(request)
except:
self.handle_error(request, client_address)
self.shutdown_request(request)

def process_request(self, request, client_address):
“””Start a new thread to process the request.”””
t = threading.Thread(target = self.process_request_thread,
args = (request, client_address))
t.daemon = self.daemon_threads
t.start()
`

ThreadingMixIn

`
class BaseRequestHandler:

“””Base class for request handler classes.

This class is instantiated for each request to be handled. The
constructor sets the instance variables request, client_address
and server, and then calls the handle() method. To implement a
specific service, all you need to do is to derive a class which
defines a handle() method.

The handle() method can find the request as self.request, the
client address as self.client_address, and the server (in case it
needs access to per-server information) as self.server. Since a
separate instance is created for each request, the handle() method
can define arbitrary other instance variariables.

“””

def __init__(self, request, client_address, server):
self.request = request
self.client_address = client_address
self.server = server
self.setup()
try:
self.handle()
finally:
self.finish()

def setup(self):
pass

def handle(self):
pass

def finish(self):
pass
`

SocketServer.BaseRequestHandler

SocketServer 的 ThreadingTCPServer 之所以能够同时解决申请得益于 select 和 Threading 两个货色，其实实质上就是在服务器端为每一个客户端创立一个线程，以后线程用来解决对应客户端的申请，所以，能够反对同时 n 个客户端链接（长连贯）。

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