陈硕 (giantchen_AT_gmail)
Blog.csdn.net/Solstice
这是《Muduo 网络编程示例》系列的第四篇文章。
Muduo 全系列文章列表： http://blog.csdn.net/Solstice/category/779646.aspx
Python Twisted 是一款非常好的网络库，它也采用 Reactor 作为网络编程的基本模型，所以从使用上与 muduo 颇有相似之处。（当然，muduo 没有 deferreds）Finger 是 twisted 文档的一个经典例子，本文展示如何用 muduo 来实现最简单的 finger 服务端。限于篇幅，只实现 finger01~07。代码位于 examples/twisted/finger 。
1 拒绝连接
什么都不做，程序空等。finger01.cc
1: #include <muduo/net/EventLoop.h>
2:
3: using namespace muduo;
4: using namespace muduo::net;
5:
6: int main()
7: { 8: EventLoop loop;
9: loop.loop();
10: }
2 接受新连接
在 1079 端口侦听新连接，接受连接之后什么都不做，程序空等。muduo 会自动丢弃收到的数据。finger02.cc
1: #include <muduo/net/EventLoop.h>
2: #include <muduo/net/TcpServer.h>
3:
4: using namespace muduo;
5: using namespace muduo::net;
6:
7: int main()
8: { 9: EventLoop loop;
10: TcpServer server(&loop, InetAddress(1079), "Finger");
11: server.start();
12: loop.loop();
13: }
3 主动断开连接
接受新连接之后主动断开。finger03.cc
以下省略头文件和 namespace。
1: void onConnection(const TcpConnectionPtr& conn)
2: { 3: if (conn->connected())
4: { 5: conn->shutdown();
6: }
7: }
8:
9: int main()
10: { 11: EventLoop loop;
12: TcpServer server(&loop, InetAddress(1079), "Finger");
13: server.setConnectionCallback(onConnection);
14: server.start();
15: loop.loop();
16: }
4 读取用户名，然后断开连接
如果读到一行以 \r\n 结尾的消息，就断开连接。finger04.cc
注意这段代码有安全问题，如果恶意客户端不断发送数据而不换行，会撑爆服务端的内存。另外，Buffer::findCRLF() 是线性查找，如果客户端每次发一个字节，服务端的时间复杂度为 O(N^2)，会消耗 CPU 资源。
1: void onMessage(const TcpConnectionPtr& conn,
2: Buffer* buf,
3: Timestamp receiveTime)
4: { 5: if (buf->findCRLF())
6: { 7: conn->shutdown();
8: }
9: }
10:
11: int main()
12: { 13: EventLoop loop;
14: TcpServer server(&loop, InetAddress(1079), "Finger");
15: server.setMessageCallback(onMessage);
16: server.start();
17: loop.loop();
18: }
5. 读取用户名、输出错误信息、然后断开连接
如果读到一行以 \r\n 结尾的消息，就发送一条出错信息，然后断开连接。finger05.cc
安全问题同上。
1: void onMessage(const TcpConnectionPtr& conn,
2: Buffer* buf,
3: Timestamp receiveTime)
4: { 5: if (buf->findCRLF())
6: { 7: conn->send("No such user\r\n"); 8: conn->shutdown();
9: }
10: }
11:
12: int main()
13: { 14: EventLoop loop;
15: TcpServer server(&loop, InetAddress(1079), "Finger");
16: server.setMessageCallback(onMessage);
17: server.start();
18: loop.loop();
19: }
6. 从空的 UserMap 里查找用户
从一行消息中拿到用户名（第 22 行），在 UserMap 里查找，然后返回结果。finger06.cc
安全问题同上。
1: typedef std::map<string, string> UserMap;
2: UserMap users;
3:
4: string getUser(const string& user)
5: { 6: string result = "No such user";
7: UserMap::iterator it = users.find(user);
8: if (it != users.end())
9: { 10: result = it->second;
11: }
12: return result;
13: }
14:
15: void onMessage(const TcpConnectionPtr& conn,
16: Buffer* buf,
17: Timestamp receiveTime)
18: { 19: const char* crlf = buf->findCRLF();
20: if (crlf)
21: { 22: string user(buf->peek(), crlf);
23: conn->send(getUser(user) + "\r\n");
24: buf->retrieveUntil(crlf + 2);
25: conn->shutdown();
26: }
27: }
28:
29: int main()
30: { 31: EventLoop loop;
32: TcpServer server(&loop, InetAddress(1079), "Finger");
33: server.setMessageCallback(onMessage);
34: server.start();
35: loop.loop();
36: }
7. 往 UserMap 里添加一个用户
与前面几乎完全一样，只多了第 31 行。finger07.cc
1: typedef std::map<string, string> UserMap;
2: UserMap users;
3:
4: string getUser(const string& user)
5: { 6: string result = "No such user";
7: UserMap::iterator it = users.find(user);
8: if (it != users.end())
9: { 10: result = it->second;
11: }
12: return result;
13: }
14:
15: void onMessage(const TcpConnectionPtr& conn,
16: Buffer* buf,
17: Timestamp receiveTime)
18: { 19: const char* crlf = buf->findCRLF();
20: if (crlf)
21: { 22: string user(buf->peek(), crlf);
23: conn->send(getUser(user) + "\r\n");
24: buf->retrieveUntil(crlf + 2);
25: conn->shutdown();
26: }
27: }
28:
29: int main()
30: { 31: users["schen"] = "Happy and well";
32: EventLoop loop;
33: TcpServer server(&loop, InetAddress(1079), "Finger");
34: server.setMessageCallback(onMessage);
35: server.start();
36: loop.loop();
37: }
以上就是全部内容，可以用 telnet 扮演客户端来测试我们的简单 finger 服务端。
Telnet 测试
在一个命令行窗口运行
$ ./bin/twisted_finger07
另一个命令行运行
$ telnet localhost 1079
Trying ::1...
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
muduo
No such user
Connection closed by foreign host.
再试一次
$ telnet localhost 1079
Trying ::1...
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
schen
Happy and well
Connection closed by foreign host.
冒烟测试过关。
(待续)