Boost实现简单的udp代理服务器

[来源] 达内    [编辑] 达内   [时间]2012-10-16

这段时间在开发代理服务器,这方面的资料了解的比较多,这里我总结下udp代理服务的实现,也方便我以后查阅

这段时间在开发代理服务器,这方面的资料了解的比较多,这里我总结下udp代理服务的实现,也方便我以后查阅。

< h1 style="margin: 0px; padding: 0px; font-weight: bold; color: rgb(0, 0, 0); line-height: 1.5; font-family: verdana, Arial, Helvetica, sans-serif; font-style: normal; font-variant: normal; letter-spacing: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); " class="cjk"> 一、通信模型 < p lang="zh-CN" style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> 1、非代理情况下的通信模型

< p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">

< p lang="zh-CN" style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> 这是典型的C-S通信模型,客户端和服务器直接交互。

< p lang="zh-CN" style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> 2、代理情况下的通信模型

< p style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">

< p lang="zh-CN" style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> 这种情况下,服务器和客户端不是直接交互,而是通过代理服务器进行的,代理服务器负责把客户端发来的请求转发给服务器,并把服务的回应返回给客户端。

< h1 style="margin: 0px; padding: 0px; font-weight: bold; color: rgb(0, 0, 0); line-height: 1.5; font-family: verdana, Arial, Helvetica, sans-serif; font-style: normal; font-variant: normal; letter-spacing: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); " class="cjk">二、 UDP服务器和客户端 demo < p lang="zh-CN" style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> 上面分析了通信模型,这里给出一个echo的服务器和客户端代码以供下文使用。

< p lang="zh-CN" style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> 1、服务端demo

< p lang="zh-CN" style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> 这里有一个python实现的echo服务器,代码如下:

< div style="margin: 5px 0px; padding: 5px; background-color: rgb(245, 245, 245); font-family: 'Courier New'; font-size: 12px; border: 1px solid rgb(204, 204, 204); overflow: auto; color: rgb(51, 51, 51); font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; " class="cnblogs_code">
#
! /usr/bin/python #
 a simple udp server

import socket, traceback  s 
= socket.socket(socket.AF_INET, socket.SOCK_DGRAM) s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 
1) s.bind(("
192.168.1.100"
,12345))  while
 True:     try


:         message, address = s.recvfrom(1024)         
print "
Got data from"


, address         print
 message         s.sendto(message, address)     except
 (KeyboardInterrupt, SystemExit):         
raise


    except
:         traceback.print_exc()
< p lang="zh-CN" style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> 服务端把收到的数据输出并发给客户端。

< p lang="zh-CN" style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> 2、客户端demo 

< div style="margin: 5px 0px; padding: 5px; background-color: rgb(245, 245, 245); font-family: 'Courier New'; font-size: 12px; border: 1px solid rgb(204, 204, 204); overflow: auto; color: rgb(51, 51, 51); font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; " class="cnblogs_code">
#
! /usr/bin/python #
 a simple udp client

import socket,time  client 
= socket.socket(socket.AF_INET, socket.SOCK_DGRAM) client.connect((
'192.168.1.100
', 12345))  
while

 True:         client.sendall('
3'
)         print
 time.time(),' : send success
'

        print time.time(),
" : "
,client.recv(1024)         time.sleep(3
) 

#client.close()
< p lang="zh-CN" style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">  客户端负责给服务端发数据并接收服务器返回的数据。

< h1 style="margin: 0px; padding: 0px; font-weight: bold; color: rgb(0, 0, 0); line-height: 1.5; font-family: verdana, Arial, Helvetica, sans-serif; font-style: normal; font-variant: normal; letter-spacing: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); " class="cjk">三、 UDP代理服务器 demo < p lang="zh-CN" style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> 这里采用boost库实现,用asio中的异步机制。

< p lang="zh-CN" style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> 1、成员变量及参数说明

< p lang="zh-CN" style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> 类名称: m_udpProxyServer

< p lang="zh-CN" style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); ">私有成员:

< p lang="zh-CN" style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> ip::udp::socket downstream_socket_; //代理服务器和客户端的链接

< p lang="zh-CN" style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> ip::udp::socket upstream_socket_; //代理服务器和远端服务器(echo server)的链接

< p lang="zh-CN" style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> string _remotehost; // 远端服务器(echo server )的ip地址

< p lang="zh-CN" style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> int _remoteport; //远端服务器(echo server)的端口

< p lang="zh-CN" style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> ip::udp::endpoint downstream_remoteUdpEndpoint; //客户端信息

< p lang="zh-CN" style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> ip::udp::endpoint upstream_remoteUdpEndpoint; //服务端信息

< p lang="zh-CN" style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> unsigned char downstream_data_[max_data_length]; //上传链路buffer

< p lang="zh-CN" style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> unsigned char upstream_data_[max_data_length]; //下载链路buffer

< p lang="zh-CN" style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> 2、启动本地服务

< p lang="zh-CN" style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> 代理服务器在这个模型中既充当客户端的服务器,又充当远端服务器(echo server )的客户端,所以代理服务器既要有本地监听端口供客户端连接,又要向远端服务器(echo server)发起链接,转发客户端发来的数据。

< div style="margin: 5px 0px; padding: 5px; background-color: rgb(245, 245, 245); font-family: 'Courier New'; font-size: 12px; border: 1px solid rgb(204, 204, 204); overflow: auto; color: rgb(51, 51, 51); font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; " class="cnblogs_code"> View Code
< p lang="zh-CN" style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> 3、连接远端服务器

< p lang="zh-CN" style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> 当接收到客户端发来的数据后,触发代理服务器向远端服务器的连接。

< div style="margin: 5px 0px; padding: 5px; background-color: rgb(245, 245, 245); font-family: 'Courier New'; font-size: 12px; border: 1px solid rgb(204, 204, 204); overflow: auto; color: rgb(51, 51, 51); font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; " class="cnblogs_code"> View Code
< p lang="zh-CN" style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> 4、数据转发

< p lang="zh-CN" style="margin: 10px auto; padding: 0px; text-indent: 0px; color: rgb(51, 51, 51); font-family: verdana, Arial, Helvetica, sans-serif; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: 25px; orphans: 2; text-align: -webkit-auto; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); "> 将从客户端接收到的数据转发给远端服务器,并接收远端服务器的返回数据,转发给客户端。

< div style="margin: 5px 0px; padding: 5px; background-color: rgb(245, 245, 245); font-family: 'Courier New'; font-size: 12px; border: 1px solid rgb(204, 204, 204); overflow: auto; color: rgb(51, 51, 51); font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; " class="cnblogs_code"> View Code
复制代码
void
 handle_upstream_connect(const
 size_t&

 bytes_transferred,     const
 boost::system::error_code& error) {     
//

将从客户端接收到的数据转发给远端服务器


    upstream_socket_.async_send_to(             boost::asio::buffer(downstream_data_,bytes_transferred),             upstream_remoteUdpEndpoint,             boost::bind(
&m_udpProxyServer::handle_upstream_send,             

this
,boost::asio::placeholders::error)); }  

void handle_upstream_send(
const

 boost::system::error_code& error) {     
if

 (!error )     {                 
//

从服务器接收返回数据


        upstream_socket_.async_receive_from(             boost::asio::buffer(upstream_data_,max_data_length),             upstream_remoteUdpEndpoint,             boost::bind(
&m_udpProxyServer::handle_upstream_receive,             

this
,                                 boost::asio::placeholders::bytes_transferred,             boost::asio::placeholders::error));      }     else


     {         std::cerr << "
Error: 

"
 << error.message() << std::endl;     } }  
void

 handle_upstream_receive(const
 size_t& bytes_transferred,     

const boost::system::error_code&
 error) {     

if (!
error )     {                     

//
把从服务器接收到的返回数据转发给客户端



        downstream_socket_.async_send_to(             boost::asio::buffer(upstream_data_,bytes_transferred),             downstream_remoteUdpEndpoint,             boost::bind(
&m_udpProxyServer::handle_downstream_send,             

this
,             boost::asio::placeholders::error));     }     

else     {         std::cerr 
<< "Error: 
"
 << error.message() << std::endl;     } }  

void handle_downstream_send(
const

 boost::system::error_code& error) {     
if

 (!error )     {                 
//

接收客户端发来的数据


        downstream_socket_.async_receive_from(             boost::asio::buffer(downstream_data_,max_data_length),             downstream_remoteUdpEndpoint,             boost::bind(
&m_udpProxyServer::handle_downstream_receive,this

,             boost::asio::placeholders::bytes_transferred,             boost::asio::placeholders::error));     }     
else

     {         std::cerr << 
"

Error: "
 << error.message() << std::endl;     } }  


void handle_downstream_receive(const
 size_t& bytes_transferred,     
const

 boost::system::error_code& error) {     
//

将从客户端接收到的数据转发给远端服务器

    upstream_socket_.async_send_to(         boost::asio::buffer(downstream_data_,bytes_transferred),         upstream_remoteUdpEndpoint,         boost::bind(
&m_udpProxyServer::handle_upstream_send,         
this
,boost::asio::placeholders::error)); }
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