这里的代理服务器，是指二级代理服务器。比如：A可以访问B，B可以访问C，A不能直接访问C。这时，如果在B开一个二级代理，就可实现A访问C。现有的工具有CCProxy。

这里就是使用Python简单的实现一个二级代理。

#coding=utf-8     import socket     import select     import sys     import threading    import time    import logging    import os    logsDir = "logs"    if not os.path.isdir(logsDir):        os.mkdir(logsDir)            logging.basicConfig(level=logging.DEBUG,                    format='%(asctime)s %(filename)s[line:%(lineno)d] %(levelname)s %(message)s',                    datefmt='%a, %d %b %Y %H:%M:%S',                    filename='logs/logs.log',                    filemode='a')         #C的IP和端口     to_addr = ('0.0.0.0', 8087)        class Proxy:         def __init__(self, addr):             self.proxy = socket.socket(socket.AF_INET, socket.SOCK_STREAM)             self.proxy.bind(addr)             self.proxy.listen(10)             self.inputs = [self.proxy]             self.route = {}                def serve_forever(self):             logging.info('proxy listen...')            while 1:                 readable, _, _ = select.select(self.inputs, [], [])                 for self.sock in readable:                     if self.sock == self.proxy:                         self.on_join()                     else:                        try:                            data = self.sock.recv(8192)                        except Exception, e:                            logging.error(str(e))                            self.on_quit()                            continue                                                if not data:                             self.on_quit()                         else:                            try:                                self.route[self.sock].send(data)                            except Exception, e:                                logging.error(str(e))                                self.on_quit()                                continue               def on_join(self):             client, addr = self.proxy.accept()             logging.info("proxy client " + str(addr) + 'connect')            forward = socket.socket(socket.AF_INET, socket.SOCK_STREAM)             forward.connect(to_addr)             self.inputs += [client, forward]             self.route[client] = forward             self.route[forward] = client                 #删除连接        def on_quit(self):            ls = [self.sock]            if self.sock in self.route:                ls.append(self.route[self.sock])            for s in ls:                if s in self.inputs:                    self.inputs.remove(s)                if s in self.route:                    del self.route[s]                 s.close()                     if __name__ == "__main__":        try:             Proxy(('', 8192)).serve_forever()        except KeyboardInterrupt:             logging.error("KeyboardInterrupt")            return      

来自：http://blog.csdn.net/junfeng_feng/article/details/42966363