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Muduo 网络编程示例之一:五个简单 TCP 协议

陈硕 (giantchen_AT_gmail)

Blog.csdn.net/Solstice

这是《Muduo 网络编程示例》系列的第一篇文章。

全系列文章列表: http://blog.csdn.net/Solstice/category/779646.aspx

本文将介绍第一个示例:五个简单 TCP 网络服务协议,包括 echo (RFC 862)、discard (RFC 863)、chargen (RFC 864)、daytime (RFC 867)、time (RFC 868),以及 time 协议的客户端。各协议的功能简介如下:

  • discard - 丢弃所有收到的数据;
  • daytime - 服务端 accept 连接之后,以字符串形式发送当前时间,然后主动断开连接;
  • time - 服务端 accept 连接之后,以二进制形式发送当前时间(从 Epoch 到现在的秒数),然后主动断开连接;我们需要一个客户程序来把收到的时间转换为字符串。
  • echo - 回显服务,把收到的数据发回客户端;
  • chargen - 服务端 accept 连接之后,不停地发送测试数据。

以上五个协议使用不同的端口,可以放到同一个进程中实现,且不必使用多线程。完整的代码见 muduo/examples/simple,下载地址 http://muduo.googlecode.com/files/muduo-0.1.6-alpha.tar.gz

discard

Discard 恐怕算是最简单的长连接 TCP 应用层协议,它只需要关注“三个半事件”中的“消息/数据到达”事件,事件处理函数如下:

   1: void DiscardServer::onMessage(const muduo::net::TcpConnectionPtr& conn,
   2:                  muduo::net::Buffer* buf,
   3:                  muduo::Timestamp time)
   4: {
   5:   string msg(buf->retrieveAsString());  // 取回读到的全部数据
   6:   LOG_INFO << conn->name() << " discards " << msg.size() << " bytes at " << time.toString();
   7: }
剩下的都是例行公事的代码:
定义一个 DiscardServer class,以 TcpServer 为成员。
   1: #ifndef MUDUO_EXAMPLES_SIMPLE_DISCARD_DISCARD_H
   2: #define MUDUO_EXAMPLES_SIMPLE_DISCARD_DISCARD_H
   3:  
   4: #include <muduo/net/TcpServer.h>
   5:  
   6: // RFC 863
   7: class DiscardServer
   8: {
   9:  public:
  10:   DiscardServer(muduo::net::EventLoop* loop,
  11:                 const muduo::net::InetAddress& listenAddr);
  12:  
  13:   void start();
  14:  
  15:  private:
  16:   void onConnection(const muduo::net::TcpConnectionPtr& conn);
  17:  
  18:   void onMessage(const muduo::net::TcpConnectionPtr& conn,
  19:                  muduo::net::Buffer* buf,
  20:                  muduo::Timestamp time);
  21:  
  22:   muduo::net::EventLoop* loop_;
  23:   muduo::net::TcpServer server_;
  24: };
  25:  
  26: #endif  // MUDUO_EXAMPLES_SIMPLE_DISCARD_DISCARD_H
注册回调函数
   1: DiscardServer::DiscardServer(muduo::net::EventLoop* loop,
   2:                              const muduo::net::InetAddress& listenAddr)
   3:   : loop_(loop),
   4:     server_(loop, listenAddr, "DiscardServer")
   5: {
   6:   server_.setConnectionCallback(
   7:       boost::bind(&DiscardServer::onConnection, this, _1));
   8:   server_.setMessageCallback(
   9:       boost::bind(&DiscardServer::onMessage, this, _1, _2, _3));
  10: }
  11:  
  12: void DiscardServer::start()
  13: {
  14:   server_.start();
  15: }
处理连接与数据事件
   1: void DiscardServer::onConnection(const muduo::net::TcpConnectionPtr& conn)
   2: {
   3:   LOG_INFO << "DiscardServer - " << conn->peerAddress().toHostPort() << " -> "
   4:     << conn->localAddress().toHostPort() << " is "
   5:     << (conn->connected() ? "UP" : "DOWN");
   6: }
   7:  
   8: void DiscardServer::onMessage(const muduo::net::TcpConnectionPtr& conn,
   9:                  muduo::net::Buffer* buf,
  10:                  muduo::Timestamp time)
  11: {
  12:   string msg(buf->retrieveAsString());
  13:   LOG_INFO << conn->name() << " discards " << msg.size() << " bytes at " << time.toString();
  14: }
在 main() 里用 EventLoop 让整个程序转起来
   1: #include "discard.h"
   2:  
   3: #include <muduo/base/Logging.h>
   4: #include <muduo/net/EventLoop.h>
   5:  
   6: using namespace muduo;
   7: using namespace muduo::net;
   8:  
   9: int main()
  10: {
  11:   LOG_INFO << "pid = " << getpid();
  12:   EventLoop loop;
  13:   InetAddress listenAddr(2009);
  14:   DiscardServer server(&loop, listenAddr);
  15:   server.start();
  16:   loop.loop();
  17: }

daytime

Daytime 是短连接协议,在发送完当前时间后,由服务端主动断开连接。它只需要关注“三个半事件”中的“连接已建立”事件,事件处理函数如下:

   1: void DaytimeServer::onConnection(const muduo::net::TcpConnectionPtr& conn)
   2: {
   3:   LOG_INFO << "DaytimeServer - " << conn->peerAddress().toHostPort() << " -> "
   4:     << conn->localAddress().toHostPort() << " is "
   5:     << (conn->connected() ? "UP" : "DOWN");
   6:   if (conn->connected())
   7:   {
   8:     conn->send(Timestamp::now().toFormattedString() + "\n"); // 发送时间字符串
   9:     conn->shutdown(); // 主动断开连接
  10:   }
  11: }

剩下的都是例行公事的代码,为节省篇幅,此处从略,请阅读 muduo/examples/simple/daytime。

用 netcat 扮演客户端,运行结果如下:

$ nc 127.0.0.1 2013
2011-02-02 03:31:26.622647    # 服务器返回的时间字符串

time

Time 协议与 daytime 极为类似,只不过它返回的不是日期时间字符串,而是一个 32-bit 整数,表示从 1970-01-01 00:00:00Z 到现在的秒数。当然,这个协议有“2038 年问题”。服务端只需要关注“三个半事件”中的“连接已建立”事件,事件处理函数如下:

   1: void TimeServer::onConnection(const muduo::net::TcpConnectionPtr& conn)
   2: {
   3:   LOG_INFO << "TimeServer - " << conn->peerAddress().toHostPort() << " -> "
   4:     << conn->localAddress().toHostPort() << " is "
   5:     << (conn->connected() ? "UP" : "DOWN");
   6:   if (conn->connected())
   7:   {
   8:     int32_t now = sockets::hostToNetwork32(static_cast<int>(::time(NULL)));
   9:     conn->send(&now, sizeof now);  // 发送 4 个字节
  10:     conn->shutdown();  // 主动断开连接
  11:   }
  12: }

剩下的都是例行公事的代码,为节省篇幅,此处从略,请阅读 muduo/examples/simple/time。

用 netcat 扮演客户端,并用 hexdump 来打印二进制数据,运行结果如下:

$ nc 127.0.0.1 2037 | hexdump -C
00000000  4d 48 d0 d5                                       |MHÐÕ|
00000004

 

time_client

因为 time 服务端发送的是二进制数据,不便直接阅读,我们编写一个客户端来解析并打印收到的 4 个字节数据。这个程序只需要关注“三个半事件”中的“消息/数据到达”事件,事件处理函数如下:

   1: void TimeClient::onMessage(const TcpConnectionPtr& conn, Buffer* buf, Timestamp receiveTime)
   2: {
   3:   if (buf->readableBytes() >= sizeof(int32_t))
   4:   {
   5:     const void* data = buf->peek();
   6:     int32_t time = *static_cast<const int32_t*>(data);
   7:     buf->retrieve(sizeof(int32_t));
   8:     time_t servertime = sockets::networkToHost32(time);
   9:     Timestamp t(servertime * Timestamp::kMicroSecondsPerSecond);
  10:     LOG_INFO << "Server time = " << servertime << ", " << t.toFormattedString();
  11:   }
  12:   else
  13:   {
  14:     LOG_INFO << conn->name() << " no enough data " << buf->readableBytes()
  15:      << " at " << receiveTime.toFormattedString();
  16:   }
  17: }

注意其中考虑到了如果数据没有一次性收全,已经收到的数据会暂存在 Buffer 里,以等待下一次机会,程序也不会阻塞。这样即便服务器一个字节一个字节地发送数据,代码还是能正常工作,这也是非阻塞网络编程必须在用户态使用接受缓冲的主要原因。

这是我们第一次用到 TcpClient class,完整的代码如下:

   1: #include <muduo/base/Logging.h>
   2: #include <muduo/net/EventLoop.h>
   3: #include <muduo/net/InetAddress.h>
   4: #include <muduo/net/SocketsOps.h>
   5: #include <muduo/net/TcpClient.h>
   6:  
   7: #include <boost/bind.hpp>
   8:  
   9: #include <utility>
  10:  
  11: #include <stdio.h>
  12: #include <unistd.h>
  13:  
  14: using namespace muduo;
  15: using namespace muduo::net;
  16:  
  17: class TimeClient : boost::noncopyable
  18: {
  19:  public:
  20:   TimeClient(EventLoop* loop, const InetAddress& listenAddr)
  21:     : loop_(loop),
  22:       client_(loop, listenAddr, "TimeClient")
  23:   {
  24:     client_.setConnectionCallback(
  25:         boost::bind(&TimeClient::onConnection, this, _1));
  26:     client_.setMessageCallback(
  27:         boost::bind(&TimeClient::onMessage, this, _1, _2, _3));
  28:     // client_.enableRetry();
  29:   }
  30:  
  31:   void connect()
  32:   {
  33:     client_.connect();
  34:   }
  35:  
  36:  private:
  37:   void onConnection(const TcpConnectionPtr& conn)
  38:   {
  39:     LOG_INFO << conn->localAddress().toHostPort() << " -> "
  40:         << conn->peerAddress().toHostPort() << " is "
  41:         << (conn->connected() ? "UP" : "DOWN");
  42:  
  43:     if (!conn->connected())  // 如果连接断开,则终止主循环,退出程序
  44:       loop_->quit();
  45:   }
  46:  
  47:   void onMessage(const TcpConnectionPtr& conn, Buffer* buf, Timestamp receiveTime)
  48:   {
  49:     if (buf->readableBytes() >= sizeof(int32_t))
  50:     {
  51:       const void* data = buf->peek();
  52:       int32_t time = *static_cast<const int32_t*>(data);
  53:       buf->retrieve(sizeof(int32_t));
  54:       time_t servertime = sockets::networkToHost32(time);
  55:       Timestamp t(servertime * Timestamp::kMicroSecondsPerSecond);
  56:       LOG_INFO << "Server time = " << servertime << ", " << t.toFormattedString();
  57:     }
  58:     else
  59:     {
  60:       LOG_INFO << conn->name() << " no enough data " << buf->readableBytes()
  61:        << " at " << receiveTime.toFormattedString();
  62:     }
  63:   }
  64:  
  65:   EventLoop* loop_;
  66:   TcpClient client_;
  67: };
  68:  
  69: int main(int argc, char* argv[])
  70: {
  71:   LOG_INFO << "pid = " << getpid();
  72:   if (argc > 1)
  73:   {
  74:     EventLoop loop;
  75:     InetAddress serverAddr(argv[1], 2037);
  76:  
  77:     TimeClient timeClient(&loop, serverAddr);
  78:     timeClient.connect();
  79:     loop.loop();
  80:   }
  81:   else
  82:   {
  83:     printf("Usage: %s host_ip\n", argv[0]);
  84:   }
  85: }

程序的运行结果如下,假设 time server 运行在本机:

$ ./simple_timeclient 127.0.0.1
2011-02-02 04:10:35.181717  4296 INFO pid = 4296 - timeclient.cc:71
2011-02-02 04:10:35.183668  4296 INFO TcpClient::connect[TimeClient] - connecting to 127.0.0.1:2037 - TcpClient.cc:60
2011-02-02 04:10:35.185178  4296 INFO 127.0.0.1:40960 -> 127.0.0.1:2037 is UP - timeclient.cc:39
2011-02-02 04:10:35.185279  4296 INFO Server time = 1296619835, 2011-02-02 04:10:35.000000 - timeclient.cc:56
2011-02-02 04:10:35.185354  4296 INFO 127.0.0.1:40960 -> 127.0.0.1:2037 is DOWN - timeclient.cc:39

 

echo

Echo 是我们遇到的第一个带交互的协议:服务端把客户端发过来的数据原封不动地传回去。它只需要关注“三个半事件”中的“消息/数据到达”事件,事件处理函数如下:

   1: void EchoServer::onMessage(const TcpConnectionPtr& conn,
   2:                            Buffer* buf,
   3:                            Timestamp time)
   4: {
   5:   string msg(buf->retrieveAsString());
   6:   LOG_INFO << conn->name() << " echo " << msg.size() << " bytes at " << time.toString();
   7:   conn->send(msg);
   8: }

这段代码实现的不是行回显(line echo)服务,而是有一点数据就发送一点数据。这样可以避免客户端恶意地不发送换行字符,而服务端又必须缓存已经收到的数据,导致服务器内存暴涨。但这个程序还是有一个安全漏洞,即如果客户端故意不断发生数据,但从不接收,那么服务端的发送缓冲区会一直堆积,导致内存暴涨。解决办法可以参考下面的 chargen 协议。

剩下的都是例行公事的代码,为节省篇幅,此处从略,请阅读 muduo/examples/simple/echo。

练习 1:修改 EchoServer::onMessage(),实现大小写互换。

练习 2:修改 EchoServer::onMessage(),实现 rot13 加密。

chargen

Chargen 协议很特殊,它只发送数据,不接收数据。而且,它发送数据的速度不能快过客户端接收的速度,因此需要关注“三个半事件”中的半个“消息/数据发送完毕”事件(onWriteComplete),事件处理函数如下:

   1: void ChargenServer::onConnection(const muduo::net::TcpConnectionPtr& conn)
   2: {
   3:   LOG_INFO << "ChargenServer - " << conn->peerAddress().toHostPort() << " -> "
   4:     << conn->localAddress().toHostPort() << " is "
   5:     << (conn->connected() ? "UP" : "DOWN");
   6:   if (conn->connected())
   7:   {
   8:     conn->send(message_);  // 在连接建立时发生第一次数据
   9:   }
  10: }
  11:  
  12: void ChargenServer::onMessage(const muduo::net::TcpConnectionPtr& conn,
  13:                  muduo::net::Buffer* buf,
  14:                  muduo::Timestamp time)
  15: {
  16:   string msg(buf->retrieveAsString());
  17:   LOG_INFO << conn->name() << " discards " << msg.size() << " bytes at " << time.toString();
  18: }
  19:  
  20: void ChargenServer::onWriteComplete(const TcpConnectionPtr& conn)
  21: {
  22:   transferred_ += message_.size();
  23:   conn->send(message_);  // 继续发送数据
  24: }

剩下的都是例行公事的代码,为节省篇幅,此处从略,请阅读 muduo/examples/simple/chargen。

完整的 chargen 服务端还带流量统计功能,用到了定时器,我们会在下一篇文章里介绍定时器的使用,到时候再回头来看相关代码。

用 netcat 扮演客户端,运行结果如下:

$ nc localhost 2019 | head
!"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefgh
"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghi
#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghij
$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijk
%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijkl
&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklm
'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmn
()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmno
)*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnop
*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopq

Five in one

前面五个程序都用到了 EventLoop,这其实是个 Reactor,用于注册和分发 IO 事件。Muduo 遵循 one loop per thread 模型,多个服务端(TcpServer)和客户端(TcpClient)可以共享同一个 EventLoop,也可以分配到多个 EventLoop 上以发挥多核多线程的好处。这里我们把五个服务端用同一个 EventLoop 跑起来,程序还是单线程的,功能却强大了很多:

   1: #include "../chargen/chargen.h"
   2: #include "../daytime/daytime.h"
   3: #include "../discard/discard.h"
   4: #include "../echo/echo.h"
   5: #include "../time/time.h"
   6:  
   7: #include <muduo/base/Logging.h>
   8: #include <muduo/net/EventLoop.h>
   9:  
  10: #include <boost/bind.hpp>
  11:  
  12: using namespace muduo;
  13: using namespace muduo::net;
  14:  
  15: int main()
  16: {
  17:   LOG_INFO << "pid = " << getpid();
  18:   EventLoop loop;
  19:  
  20:   ChargenServer ChargenServer(&loop, InetAddress(2019));
  21:   ChargenServer.start();
  22:  
  23:   DaytimeServer daytimeServer(&loop, InetAddress(2013));
  24:   daytimeServer.start();
  25:  
  26:   DiscardServer discardServer(&loop, InetAddress(2009));
  27:   discardServer.start();
  28:  
  29:   EchoServer echoServer(&loop, InetAddress(2007));
  30:   echoServer.start();
  31:  
  32:   TimeServer timeServer(&loop, InetAddress(2037));
  33:   timeServer.start();
  34:  
  35:   loop.loop();
  36: }

 

以上几个协议的消息格式都非常简单,没有涉及 TCP 网络编程中常见的分包处理,在下一篇文章讲 Boost.Asio 的聊天服务器时我们再来讨论这个问题。

(待续)

posted on 2011-02-02 12:59 陈硕 阅读(...) 评论(...) 编辑 收藏

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