python网络编程socket /socketserver

时间:2022-12-08 22:02:28

  提起网络编程,不同于web编程,它主要是C/S架构,也就是服务器、客户端结构的。对于初学者而言,最需要理解的不是网络的概念,而是python对于网络编程都提供了些什么模块和功能。不同于计算机发展的初级阶段,程序员走到今天,已经脱离了手工打造一切,要自己实现所有细节的年代。现在提倡的是不要重复造*,而是学习别人的*怎么用,只有那些有需求或能专研的人才去设计*甚至汽车,so,这是一个速成的年代。

  因此,对于一个面向工作的python程序员,学习python的网络编程,其实学的就是那么几个模块,和你学习打游戏,word、excel没什么两样,本质上不是创造而是拿来主义,千万不要以为你需要从TCP/IP网络协议最底层开始一点一点实现所有的功能,它们都被封装在socket这个模块里。

socket概念

  我相信,所有的初学者都曾经被各种各样的标准模块和第三方模块所困扰,不知道该用哪个。同时,每个模块也包含许许多多的类,继承关系复杂,更是让人挠头。读源码看官方文档研究高手的文章更是一个漫长的过程。为什么就没有人将这些模块和类给梳理一下呢???难道这就是编程界的自我封闭和筛选机制?

  在谈及socket编程,必须知道这么几个概念:阻塞与非阻塞,同步与异步,多线程与多进程,IO多路复用与事件驱动。但是本文不打算讲这些。实际上你只需要知道两个模块三个类,就OK了,绝对速成!(以下为python3.5

  socket模块:socket类

  socketserver模块:ThreadingTCPServer、ForkingTCPServer类

  对于socket模块你必须透彻其原理,了熟于胸。但它是一个同步阻塞类型的模块,只能进行一对一的通信,在现今的计算机世界,属于最落后被淘汰的东西,基本不在实际中应用。

  socketserver模块稍微有点用,它能通过多线程或多进程的方式与多个用户同时进行通信。从字面就能看出ThreadingTCPServer类是实现的多线程,ForkingTCPServer是实现的多进程。

socket模块

  再怎么说它没用,它也是基础中的基础,不理解它的原理,那么更高级的模块就会掌握不透彻。

  socket(套接字)是什么?socket就是两个节点为了互相通信,而在各自家里装的一部”电话“

  socket模块是什么?socket模块是python内置的为了方便简单快速进行网络编程而提供的现成的”*“。它将TCP/IP协议进行了封装,你不需要知道如何进行网络通信,你只需要import socket,然后直接使用它提供的功能就好了。可以用下图来表示:

python网络编程socket /socketserver

  socket是基于C/S架构的,它的通信逻辑如下图:(借用图)

python网络编程socket /socketserver

  进行socket编程,必须写两个py文件,一个服务端,一个客户端。但是有两点必须强调:

  1. python3以后,socket传递的都是bytes类型的数据,string需要先转换一下,string.encode()即可;

另一端接收到的bytes数据想转换成string,只要bytes.decode()一下就可以。

  2. 在正常通信时,accept和recv方法是阻塞的,程序会暂停在那,一直等到有数据过来。

下面是一个例子:

#!/usr/bin/env python
# -*- coding:utf-8 -*-

import socket

ip_port = ('127.0.0.1',9999)

sk = socket.socket()
sk.bind(ip_port)
sk.listen(5)

while True:
    print('server waiting...')
    conn,addr = sk.accept()

    client_data = conn.recv(1024)
    print(client_data)
    conn.sendall('我是黄河!')

    conn.close()

socket server

#!/usr/bin/env python
# -*- coding:utf-8 -*-
import socket
ip_port = ('127.0.0.1',9999)

s = socket.socket()
s.connect(ip_port)

s.sendall('我是长江')

server_reply = s.recv(1024)
print(server_reply)

s.close()

socket client

方法分析:  

  sk = socket.socket(socket.AF_INET,socket.SOCK_STREAM,0)  实例化socket类的一个对象  

参数一:地址簇

  socket.AF_INET IPv4(默认)
  socket.AF_INET6 IPv6

  socket.AF_UNIX 只能够用于单一的Unix系统进程间通信

参数二:类型

  socket.SOCK_STREAM  流式socket , for TCP (默认)
  socket.SOCK_DGRAM   数据报式socket , for UDP

  socket.SOCK_RAW 原始套接字,普通的套接字无法处理ICMP、IGMP等网络报文,而SOCK_RAW可以;其次,SOCK_RAW也可以处理特殊的IPv4报文;此外,利用原始套接字,可以通过IP_HDRINCL套接字选项由用户构造IP头。
  socket.SOCK_RDM 是一种可靠的UDP形式,即保证交付数据报但不保证顺序。SOCK_RAM用来提供对原始协议的低级访问,在需要执行某些特殊操作时使用,如发送ICMP报文。SOCK_RAM通常仅限于高级用户或管理员运行的程序使用。
  socket.SOCK_SEQPACKET 可靠的连续数据包服务

参数三:协议

  0  (默认)与特定的地址家族相关的协议,如果是 0 ,则系统就会根据地址格式和套接类别,自动选择一个合适的协议

下面是一个UDP协议的例子,注意其中没有accept和connect的概念。

# 服务端
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)

# 客户端
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(inp,ip_port)

sk.close()

UDP Demo

  sk.bind(address)

  s.bind(address) 将套接字绑定到地址。address地址的格式取决于地址族。在AF_INET下,以元组(host,port)的形式表示地址。

sk.listen(backlog)

  开始监听传入连接。backlog指定在拒绝连接之前,可以挂起的最大连接数量,也就是除了当前正在和服务器进行通信的连接外,还可以

进入链接池的连接个数。超过这个数的连接将被服务器积极拒绝,无法建立连接。backlog等于5,表示内核已经接到了连接请求,但服务器

还没有调用accept进行处理的连接个数最大为5,这个值不能无限大,因为要在内核中维护连接队列

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。socket由阻塞变成非阻塞模式的关键参数!

sk.accept()

  接受连接并返回(conn,address),其中conn是新的套接字对象,可以用来接收和发送数据。address是连接客户端的地址。

  接收TCP 客户的连接(阻塞式)等待连接的到来

sk.connect(address)

  连接到address处的套接字。一般,address的格式为元组(hostname,port),如果连接出错,返回socket.error错误。

sk.connect_ex(address)

  同上,只不过会有返回值,连接成功时返回 0 ,连接失败时候返回编码,例如:10061

sk.close()

  关闭套接字

sk.recv(bufsize[,flag])

  接受套接字的数据。数据以字符串形式返回,bufsize指定最多可以接收的数量。flag提供有关消息的其他信息,通常可以忽略。

sk.recvfrom(bufsize[.flag])

  与recv()类似,但返回值是(data,address)。其中data是包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中的数据发送到连接的套接字。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部发送。

sk.sendall(string[,flag])

  将string中的数据发送到连接的套接字,但在返回之前会尝试发送所有数据。成功返回None,失败则抛出异常。

内部通过递归调用send,将所有内容发送出去。

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

  将数据发送到套接字,address是形式为(ipaddr,port)的元组,指定远程地址。返回值是发送的字节数。该函数主要用于UDP协议。

sk.settimeout(timeout)

  设置套接字操作的超时期,timeout是一个浮点数,单位是秒。值为None表示没有超时期。一般,超时期应该在刚创建套接字时设置,

因为它们可能用于连接的操作(如 client 连接最多等待5s )

sk.getpeername()

  返回连接套接字的远程地址。返回值通常是元组(ipaddr,port)。

sk.getsockname()

  返回套接字自己的地址。通常是一个元组(ipaddr,port)

sk.fileno()

  套接字的文件描述符

SocketServer模块

  SocketServer内部使用 IO多路复用 以及 “多线程” 和 “多进程” ,从而实现并发处理多个客户端请求的Socket服务端。即:每个客户端请求连接到服务器时,Socket服务端都会在服务器内创建一个“线程”或者“进程” 专门负责处理当前客户端的所有请求。

ThreadingTCPServer(多线程)

ThreadingTCPServer实现的Soket服务器内部会为每个client创建一个 “线程”,该线程用来和客户端进行交互。服务器相当于一个总管,在接收连接并创建新的线程后,就撒手不管了,后面的通信就是线程和客户端之间的连接了,理解这一点很重要!

1、ThreadingTCPServer基础

使用ThreadingTCPServer:

    • 创建一个继承自 SocketServer.BaseRequestHandler 的类
    • 类中必须定义一个名称为 handle 的方法
    • 启动ThreadingTCPServer
#!/usr/bin/env python
# -*- coding:utf-8 -*-
import socketserver

class MyServer(socketserver.BaseRequestHandler):

    def handle(self):
        # print self.request,self.client_address,self.server
        conn = self.request
        conn.sendall('欢迎致电 10086,请输入1xxx,0转人工服务.')
        Flag = True
        while Flag:
            data = conn.recv(1024)
            data = str(data, encoding="utf-8")
            if data == 'exit':
                Flag = False
            ':
                conn.sendall(bytes('通过可能会被录音.balabala一大推',encoding="utf-8"))
            else:
                conn.sendall(bytes('请重新输入',encoding="utf-8"))

if __name__ == '__main__':
    server = socketserver.ThreadingTCPServer(('127.0.0.1',8009),MyServer)
    server.serve_forever()

SocketServer 服务器

#!/usr/bin/env python
# -*- coding:utf-8 -*-

import socket

ip_port = ('127.0.0.1',8009)
sk = socket.socket()
sk.connect(ip_port)
sk.settimeout(5)

while True:
    data = sk.recv(1024)
    print('receive:',data)
    inp = input('please input:')
    sk.sendall(bytes(inp, encoding="utf-8"))
    if inp == 'exit':
        break

sk.close()

socketserver 客户端

  分析一下服务器端的代码,核心要点有这些:

  • 连接对象不再是socket模块中的socket.socket()了,而是self.request,这是固定语法,不可变!以后调用send和recv方法都是使用self.request
  • handle方法是整个连接的处理核心,一旦它运行结束,整个连接也就断了(但其他的线程和其他的客户端还正常),因此一般在此设置一个无限循环。
  • 在server = SocketServer.ThreadingTCPServer(('127.0.0.1',8009),MyServer)这个实例化的过程中,必须将自己创建的类,作为参数传递进去
  • server.serve_forever()表示该服务器在正常情况下将永远运行

  2、ThreadingTCPServer源码剖析

  ThreadingTCPServer类的继承关系如下:

python网络编程socket /socketserver

  内部调用流程为:

  • 启动服务端程序
  • 执行 TCPServer.__init__ 方法,创建服务端Socket对象并绑定 IP 和 端口
  • 执行 BaseServer.__init__ 方法,将自定义的继承自SocketServer.BaseRequestHandler 的类 MyRequestHandle赋值给self.RequestHandlerClass
  • 执行 BaseServer.server_forever 方法,While 循环一直监听是否有客户端请求到达 ...
  • 当客户端连接到达服务器
  • 执行 ThreadingMixIn.process_request 方法,创建一个 “线程” 用来处理请求
  • 执行 ThreadingMixIn.process_request_thread 方法
  • 执行 BaseServer.finish_request 方法,执行 self.RequestHandlerClass()  即:执行 自定义 MyRequestHandler 的构造方法(自动调用基类BaseRequestHandler的构造方法,在该构造方法中又会调用 MyRequestHandler的handle方法)

  ThreadingTCPServer相关源码:

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()

TCPServer

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 ThreadingTCPServer(ThreadingMixIn, TCPServer): pass
# 还有比这更简单,更NB的类吗

ThreadingTCPServer

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

ForkingTCPServer

ForkingTCPServer和ThreadingTCPServer的使用和执行流程基本一致,只不过在内部分别为请求者建立 “线程”  和 “进程”。

基本使用:

#!/usr/bin/env python
# -*- coding:utf-8 -*-
import socketserver

class MyServer(socketserver.BaseRequestHandler):

    def handle(self):
        # print self.request,self.client_address,self.server
        conn = self.request
        conn.sendall(bytes('欢迎致电 10086,请输入1xxx,0转人工服务.',encoding="utf-8"))
        Flag = True
        while Flag:
            data = conn.recv(1024)
            data = str(data,encoding="utf-8")
            if data == 'exit':
                Flag = False
            ':
                conn.sendall(bytes('通过可能会被录音.balabala一大推',encoding="utf-8"))
            else:
                conn.sendall(bytes('请重新输入.',encoding="utf-8"))

if __name__ == '__main__':
    server = socketserver.ForkingTCPServer(('127.0.0.1',8009),MyServer)
    server.serve_forever()

多进程socket服务器

  客户端不需要修改。所有的变化都是在服务器端。以上ForkingTCPServer只是将 ThreadingTCPServer 实例中的代码:

server = socketserver.ThreadingTCPServer(('127.0.0.1',8009),MyRequestHandler)
变更为:
server = socketserver.ForkingTCPServer(('127.0.0.1',8009),MyRequestHandler)