书上代码如下：

一个基于sockerserver的小型服务器

from socketserver import TCPServer,StreamRequestHandler

class Handler(StreamRequestHandler):

def handle(self):                  
    print(type(self.request))
    addr = self.request.getpeername()    
    print('Got connection from ',addr)
    self.wfile.write(b'thank you for connecting...')

server = TCPServer(('li-linfeng1',1234),Handler)
server.serve_forever()

我的问题是，Handler中的self.request为什么是一个socket对象呢？

self.request所在的类BaseRequestHandler源代码如下，从源代码中也看不出self.request是socket对象，求问是怎么知道这个self.request是socket对象，从而可以调用getpeername()方法的呢？

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