SocketServer源码学习(二)

SocketServer 中非常重要的两个基类就是：BaseServer 和 BaseRequestHandler
在SocketServer 中也提供了对TCP以及UDP的高级封装，这次我们主要通过分析关于TCP的处理逻辑来对SocketServer模块进行一个很好的理解和学习

TCPServer

TCPServer 继承了BaseServer，初始化的时候，进行了socket套接字的创建。

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

在这里我们看到了我们非常熟悉的关于socket的创建的内容：
self.socket = socket.socket(self.address_family, self.socket_type)
通过socket模块创建了socket对象，接着调用了server_bind和server_activate

server_bind

源码内容如下：

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()

这里我们看到了非常熟悉的操作socket.bind方法，以及设置了socket的相关属性

server_activate

源码内容如下：

def server_activate(self):"""Called by constructor to activate the server.May be overridden."""self.socket.listen(self.request_queue_size)

同样的这里的调用也非常简单就是执行了socket.listen

get_request

在TCPServer类中我们还看到了get_request方法，源码内容如下：

def get_request(self):"""Get the request and client address from the socket.May be overridden."""return self.socket.accept()

这个的调用其实我们可以在BaseServer这个基类中看到，我们之前看过关于BaseServer中这个基类的源码
我们可以从我们调用BaseServer基类中的serve_forever方法查看，这里是调用了_handle_request_noblock方法，我继续查看_handle_request_noblock这个源码

def _handle_request_noblock(self):"""Handle one request, without blocking.I assume that selector.select() has returned that the socket isreadable before this function was called, so there should be no risk ofblocking in get_request()."""try:request, client_address = self.get_request()except OSError:returnif self.verify_request(request, client_address):try:self.process_request(request, client_address)except:self.handle_error(request, client_address)self.shutdown_request(request)else:self.shutdown_request(request)

可以看到这里最后是调用了process_request来处理请求，继续查看源码：

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 finish_request(self, request, client_address):"""Finish one request by instantiating RequestHandlerClass."""self.RequestHandlerClass(request, client_address, self)

从上面的代码我们可以到最后是在finish_request中实例化了RequestHandlerClass
我们这个时候查看一下BaseRequestHandler这个基类的源码如下:

class BaseRequestHandler:"""Base class for request handler classes.This class is instantiated for each request to be handled.  Theconstructor sets the instance variables request, client_addressand server, and then calls the handle() method.  To implement aspecific service, all you need to do is to derive a class whichdefines a handle() method.The handle() method can find the request as self.request, theclient address as self.client_address, and the server (in case itneeds access to per-server information) as self.server.  Since aseparate instance is created for each request, the handle() methodcan define other arbitrary instance variables."""def __init__(self, request, client_address, server):self.request = requestself.client_address = client_addressself.server = serverself.setup()try:self.handle()finally:self.finish()def setup(self):passdef handle(self):passdef finish(self):pass

在初始化函数里我们看到了调用setup()方法，这setup在StreamRequestHandler会被重写

StreamRequestHandler

TCPServer实现了使用tcp套接字的网络服务，Handler方面则是对应的StreamRequestHandler。它继承了BaseRequestHandler。基类的setup方法和finish方法被它重写，用于通过连接实现缓存文件的读写操作。

setup方法

源码内容如下：

def setup(self):self.connection = self.requestif self.timeout is not None:self.connection.settimeout(self.timeout)if self.disable_nagle_algorithm:self.connection.setsockopt(socket.IPPROTO_TCP,socket.TCP_NODELAY, True)self.rfile = self.connection.makefile('rb', self.rbufsize)self.wfile = self.connection.makefile('wb', self.wbufsize)

这里主要设置了对应连接的属性，其中创建了两个对象非常重要:
一个可读（rfile）和一个可写（wfile）的“文件”对象
但是实际并不是创建了文件，而是封装了读取数据和发送数据的操作，抽象成了对文件的操作
可以理解：
self.rfile 就是读取客户端数据的对象，它有一些方法可以读取数据。self.wfile则是用来发送数据给客户端的对象。