一般情况下,所有的服务,都是先建立连接,也就是建立一个服务类的实例,然后开始处理用户请求,也就是建立一个请求处理类的实例。
我们分析一下源码,来看一看服务类是如何与请求处理类建立联系的。
class BaseServer:#我们创建服务类时,需要指定(地址,端口),服务处理类。 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 #…………此处省略n多代码,当我们执行server_forever方法时,里面就会调用很多服务类中的其他方法,但最终会调用finish_request方法。 def finish_request(self, request, client_address): """Finish one request by instantiating RequestHandlerClass.""" self.RequestHandlerClass(request, client_address, self) #finish_request方法中执行了self.RequestHandlerClass(request, client_address, self)。self.RequestHandlerClass是什么呢?#self.RequestHandlerClass = RequestHandlerClass(就在__init__方法中)。所以finish_request方法本质上就是创建了一个服务处理实例。 class BaseRequestHandler: 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()#当我们创建服务处理类实例时,就会运行handle()方法,而handle()方法则一般是我们处理事务逻辑的代码块。 #…………此处省略n多代码
TCPServer针对TCP套接字流
UDPServer针对UDP数据报套接字
UnixStreamServer和UnixDatagramServer针对UNIX域套接字,不常用。
他们之间的继承关系:
要实现一项服务,还必须派生一个handler class请求处理类,并重写父类的handle()方法。handle方法就是用来专门是处理请求的。该模块是通过服务类和请求处理类组合来处理请求的。
SocketServer模块提供的请求处理类有BaseRequestHandler,以及它的派生类StreamRequestHandler和DatagramRequestHandler。从名字看出可以一个处理流式套接字,一个处理数据报套接字。
请求处理类有三种方法:
setup() Called before the handle() method to perform any initialization actions required. The default implementation does nothing. 也就是在handle()之前被调用,主要的作用就是执行处理请求之前的初始化相关的各种工作。默认不会做任何事。(如果想要让其做一些事的话,就要程序员在自己的请求处理器中覆盖这个方法(因为一般自定义的请求处理器都要继承python中提供的BaseRequestHandler,ps:下文会提到的),然后往里面添加东西即可) handle() This function must do all the work required to service a request. The default implementation does nothing. Several instance attributes are available to it; the request is available as self.request; the client address as self.client_address; and the server instance as self.server, in case it needs access to per-server information. The type of self.request is different for datagram or stream services. For stream services,self.request is a socket object; for datagram services, self.request is a pair of string and socket. handle()的工作就是做那些所有与处理请求相关的工作。默认也不会做任何事。他有数个实例参数:self.request self.client_address self.server finish() Called after the handle() method to perform any clean-up actions required. The default implementation does nothing. If setup() raises an exception, this function will not be called. 在handle()方法之后会被调用,他的作用就是执行当处理完请求后的清理工作,默认不会做任何事
服务端
import socketserver class MyTCPHandler(socketserver.BaseRequestHandler): def handle(self): try: while True: self.data=self.request.recv(1024) print("{} send:".format(self.client_address),self.data) if not self.data: print("connection lost") break self.request.sendall(self.data.upper()) except Exception as e: print(self.client_address,"连接断开") finally: self.request.close() def setup(self): print("before handle,连接建立:",self.client_address) def finish(self): print("finish run after handle") if __name__=="__main__": HOST,PORT = "localhost",9988 server=socketserver.TCPServer((HOST,PORT),MyTCPHandler) server.serve_forever()
客户端
import socket client=socket.socket() client.connect(('localhost',9988)) while True: cmd=input("(quit退出)>>").strip() if len(cmd)==0: continue if cmd=="quit": break client.send(cmd.encode()) cmd_res=client.recv(1024) print(cmd_res.decode()) client.close()
异步处理
import socketserver class MyTCPHandler(socketserver.BaseRequestHandler): def handle(self): try: while True: self.data=self.request.recv(1024) print("{} send:".format(self.client_address),self.data) if not self.data: print("connection lost") break self.request.sendall(self.data.upper()) except Exception as e: print(self.client_address,"连接断开") finally: self.request.close() def setup(self): print("before handle,连接建立:",self.client_address) def finish(self): print("finish run after handle") HOST,PORT = "localhost",9999 server=socketserver.ThreadingTCPServer((HOST,PORT),MyTCPHandler)#多线程版 server.serve_forever()