muduo网络库学习之EventLoop（三）：Socket、Acceptor、TcpServer、TcpConnection（连接建立，接收消息）

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1、Socket 操作封装

Endian.h

封装了字节序转换函数（全局函数，位于muduo::net::sockets名称空间中）。

SocketsOps.h/ SocketsOps.cc

封装了socket相关系统调用（全局函数，位于muduo::net::sockets名称空间中）。

Socket.h/Socket.cc（Socket类）

用RAII方法封装socket file descriptor

InetAddress.h/InetAddress.cc（InetAddress类）

网际地址sockaddr_in封装

2、Acceptor

Acceptor用于accept(2)接受TCP连接

Acceptor的数据成员包括acceptSocket_、acceptChannel_，Acceptor的acceptSocket_是listening socket（即server socket）。

acceptChannel_用于观察acceptSocket_的readable事件，可读事件发生，Channel::handleEvent()中回调Acceptor::handleRead()，

后者调用accept(2)来接受新连接，并回调用户callback，注意callback 中传入的第一个参数是accept返回的connfd。

C++ Code  

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void Acceptor::handleRead()
{
    loop_->assertInLoopThread();
    InetAddress peerAddr( 0);
     //FIXME loop until no more
     int connfd = acceptSocket_.accept(&peerAddr);
     if (connfd >= 0)
    {
         // string hostport = peerAddr.toIpPort();
         // LOG_TRACE << "Accepts of " << hostport;
         if (newConnectionCallback_)
        {
            newConnectionCallback_(connfd, peerAddr);
        }
         else
        {
            sockets::close(connfd);
        }
    }
     else
    {
         // Read the section named "The special problem of
         // accept()ing when you can't" in libev's doc.
         // By Marc Lehmann, author of libev.
         if (errno == EMFILE)
        {
            ::close( idleFd_);
            idleFd_ = ::accept(acceptSocket_.fd(), NULL, NULL);
            ::close(idleFd_);
            idleFd_ = ::open( "/dev/null", O_RDONLY | O_CLOEXEC);
        }
    }
}

在构造函数中：

C++ Code  

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acceptChannel_.setReadCallback(
boost::bind(&Acceptor::handleRead, this));

设置用户回调函数：

C++ Code  

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// 传入connfd
typedef boost::function < void ( int sockfd,
const InetAddress &) > NewConnectionCallback;

void setNewConnectionCallback( const NewConnectionCallback &cb)
{
newConnectionCallback_ = cb;
}

开始监听：

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void Acceptor::listen()
{
    loop_->assertInLoopThread();
    listenning_ = true;
    acceptSocket_.listen();
    acceptChannel_.enableReading();
}

测试代码：

simba@ubuntu:~$ telnet 127.0.0.1 8888

C++ Code  

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#include <muduo/net/Acceptor.h>
#include <muduo/net/EventLoop.h>
#include <muduo/net/InetAddress.h>
#include <muduo/net/SocketsOps.h>

#include <stdio.h>

using namespace muduo;
using namespace muduo::net;

void newConnection( int sockfd, const InetAddress &peerAddr)
{
    printf( "newConnection(): accepted a new connection from %s\n",
           peerAddr.toIpPort().c_str());
    ::write(sockfd, "How are you?\n", 13);
    sockets::close(sockfd);
}

int main()
{
    printf( "main(): pid = %d\n", getpid());

    InetAddress listenAddr( 8888);
    EventLoop loop;

    Acceptor acceptor(&loop, listenAddr);
    acceptor.setNewConnectionCallback(newConnection);
    acceptor.listen();

    loop.loop();
}

使用telnet 连接服务器，服务器输出如下：

simba@ubuntu:~/Documents/build/debug/bin$ ./reactor_test07
20131108 07:22:30.560145Z 3960 TRACE IgnoreSigPipe Ignore SIGPIPE - EventLoop.cc:51
main(): pid = 3960
20131108 07:22:30.675116Z 3960 TRACE updateChannel fd = 4 events = 3 - EPollPoller.cc:104
20131108 07:22:30.675684Z 3960 TRACE EventLoop EventLoop created 0xBFED7324 in thread 3960 - EventLoop.cc:76
20131108 07:22:30.676073Z 3960 TRACE updateChannel fd = 5 events = 3 - EPollPoller.cc:104
20131108 07:22:30.676577Z 3960 TRACE updateChannel fd = 6 events = 3 - EPollPoller.cc:104
20131108 07:22:30.676988Z 3960 TRACE loop EventLoop 0xBFED7324 start looping - EventLoop.cc:108
20131108 07:22:40.687957Z 3960 TRACE poll nothing happended - EPollPoller.cc:74
20131108 07:22:41.606525Z 3960 TRACE poll 1 events happended - EPollPoller.cc:65
20131108 07:22:41.607053Z 3960 TRACE printActiveChannels {6: IN} - EventLoop.cc:271
newConnection(): accepted a new connection from 127.0.0.1:56409
20131108 07:22:51.617500Z 3960 TRACE poll nothing happended - EPollPoller.cc:74

telnet 端输出如下：

simba@ubuntu:~$ telnet 127.0.0.1 8888
Trying 127.0.0.1...
Connected to 127.0.0.1.
Escape character is '^]'.
How are you?
Connection closed by foreign host.
simba@ubuntu:~$

从输出可以看出，acceptSocket_.sockfd_ = 6，客户端连接上来，监听套接字发生可读事件，调用accept() 接收连接后调用用户回调函数newConnection()。

3、TcpServer/TcpConnection

Acceptor类的主要功能是socket、bind、listen

一般来说，在上层应用程序中，我们不直接使用Acceptor，而是把它作为TcpServer的成员

C++ Code  

boost::scoped_ptr<Acceptor> acceptor_; // avoid revealing Acceptor

TcpServer还包含了一个TcpConnection列表

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typedef boost::shared_ptr<TcpConnection> TcpConnectionPtr;
typedef std::map<string, TcpConnectionPtr> ConnectionMap;
ConnectionMap connections_; // 连接列表

此外，还有一个IO线程池对象和一个acceptor Eventloop*, 通过setThreadNum()设置IO线程池的线程个数（不包括main Reactor）

关于EventLoopThread, EventLoopThreadPool 类参见这里。

C++ Code  

boost::scoped_ptr<EventLoopThreadPool> threadPool_;

EventLoop* loop_; // the acceptor loop

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void TcpServer::setThreadNum( int numThreads)
{
assert( 0 <= numThreads);
threadPool_->setThreadNum(numThreads);
}

TcpConnection与Acceptor类似，有两个重要的数据成员，Socket（connfd）与Channel

C++ Code  

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boost::scoped_ptr<Socket> socket_;
boost::scoped_ptr<Channel> channel_;

时序图分析：

在TcpServer 构造函数中先初始化acceptor_成员，acceptor_(new Acceptor(loop, listenAddr))，在构造函数体内：

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// Acceptor::handleRead函数中会回调用TcpServer::newConnection
// _1对应的是socket文件描述符，_2对应的是对等方的地址(InetAddress)
acceptor_->setNewConnectionCallback(
boost::bind(&TcpServer::newConnection, this, _1, _2));

调用TcpServer::start()，开始 Acceptor::listen(), 已连接队列不为空，TcpServer:: acceptor_.acceptChannel_ 可读， poll返回，调用

Channel::handleEvent() 处理活动通道，调用Acceptor::handleRead()，函数中调用accept(2)来接受新连接，并回调TcpServer::newConnection(), 函数中先创建一个TcpConnectionPtr 对象，在TcpConnection 构造函数体中：

C++ Code  

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// 通道可读事件到来的时候，回调TcpConnection::handleRead，_1是事件发生时间
channel_->setReadCallback(
boost::bind(&TcpConnection::handleRead, this, _1));

添加进TcpServer::connections_, 设置连接回调函数和消息到来回调函数，如下：

C++ Code  

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//传入connfd
void TcpServer::newConnection( int sockfd, const InetAddress &peerAddr)
{
    ......
    TcpConnectionPtr conn( new TcpConnection(ioLoop, connName, sockfd, localAddr, peerAddr));

    connections_[connName] = conn; // conn 是TcpConnectionPtr 对象
    conn->setConnectionCallback(connectionCallback_);
    conn->setMessageCallback(messageCallback_);
    conn->connectEstablished();
}

最后调用TcpConnection::connectEstablished()

C++ Code  

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void TcpConnection::connectEstablished()
{
channel_->enableReading(); // TcpConnection所对应的通道加入到Poller关注

connectionCallback_(shared_from_this());
}

现在已经建立了一个新连接，对等方发送数据到connfd，内核接收缓冲区不为空，TcpConnection::channel_ 可读事件发生， poll返回，调用 Channel::handleEvent() 处理活动通道，调用TcpConnection:: handleRead()

C++ Code  

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void TcpConnection::handleRead(Timestamp receiveTime)
{
ssize_t n = ::read(channel_->fd(), buf, sizeof buf);
messageCallback_(shared_from_this(), buf, n);
}

shared_from_this() 会用当前对象的裸指针构造一个临时智能指针对象，引用计数加1，但马上会被析构，又减1，故无论调用多少次，对引用计数都没有影响。

测试程序：

simba@ubuntu:~$ telnet 127.0.0.1 8888

C++ Code  

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#include <muduo/net/TcpServer.h>
#include <muduo/net/EventLoop.h>
#include <muduo/net/InetAddress.h>

#include <stdio.h>

using namespace muduo;
using namespace muduo::net;

void onConnection( const TcpConnectionPtr &conn)
{
     if (conn->connected())
    {
        printf( "onConnection(): new connection [%s] from %s\n",
               conn->name().c_str(),
               conn->peerAddress().toIpPort().c_str());
    }
     else
    {
        printf( "onConnection(): connection [%s] is down\n",
               conn->name().c_str());
    }
}

void onMessage( const TcpConnectionPtr &conn,
                const char *data,
               ssize_t len)
{
    printf( "onMessage(): received %zd bytes from connection [%s]\n",
           len, conn->name().c_str());
}

int main()
{
    printf( "main(): pid = %d\n", getpid());

    InetAddress listenAddr( 8888);
    EventLoop loop;

    TcpServer server(&loop, listenAddr, "TestServer");
    server.setConnectionCallback(onConnection);
    server.setMessageCallback(onMessage);
    server.start();

    loop.loop();
}

同样地，使用telnet 去连接，服务器端输出如下：

simba@ubuntu:~/Documents/build/debug/bin$ ./reactor_test08
main(): pid = 7557
20131108 09:37:51.098888Z 7557 TRACE updateChannel fd = 4 events = 3 - EPollPoller.cc:104
20131108 09:37:51.099825Z 7557 TRACE EventLoop EventLoop created 0xBFAD3D08 in thread 7557 - EventLoop.cc:62
20131108 09:37:51.100692Z 7557 TRACE updateChannel fd = 5 events = 3 - EPollPoller.cc:104
20131108 09:37:51.101548Z 7557 TRACE updateChannel fd = 6 events = 3 - EPollPoller.cc:104
20131108 09:37:51.102063Z 7557 TRACE loop EventLoop 0xBFAD3D08 start looping - EventLoop.cc:94
20131108 09:38:01.116672Z 7557 TRACE poll nothing happended - EPollPoller.cc:74
20131108 09:38:10.616161Z 7557 TRACE poll 1 events happended - EPollPoller.cc:65
20131108 09:38:10.616774Z 7557 TRACE printActiveChannels { 6: IN} - EventLoop.cc:257
20131108 09:38:10.616894Z 7557 INFO TcpServer::newConnection [TestServer] - new connection [TestServer:0.0.0.0:8888#1] from 127.0.0.1:56410 - TcpServer.cc:93
20131108 09:38:10.617007Z 7557 DEBUG TcpConnection TcpConnection::ctor[TestServer:0.0.0.0:8888#1] at 0x827D7F8 fd=8 - TcpConnection.cc:62
20131108 09:38:10.617103Z 7557 TRACE newConnection [1] usecount=1 - TcpServer.cc:111
20131108 09:38:10.617152Z 7557 TRACE newConnection [2] usecount=2 - TcpServer.cc:113
20131108 09:38:10.617166Z 7557 TRACE connectEstablished [3] usecount=6 - TcpConnection.cc:78
20131108 09:38:10.617174Z 7557 TRACE updateChannel fd = 8 events = 3 - EPollPoller.cc:104
onConnection(): new connection [TestServer:0.0.0.0:8888#1] from 127.0.0.1:56410
20131108 09:38:10.617266Z 7557 TRACE connectEstablished [4] usecount=6 - TcpConnection.cc:83
20131108 09:38:10.617275Z 7557 TRACE newConnection [5] usecount=2 - TcpServer.cc:122
20131108 09:38:20.627567Z 7557 TRACE poll nothing happended - EPollPoller.cc:74
20131108 09:38:30.638037Z 7557 TRACE poll nothing happended - EPollPoller.cc:74
20131108 09:38:40.648523Z 7557 TRACE poll nothing happended - EPollPoller.cc:74
20131108 09:38:46.891543Z 7557 TRACE poll 1 events happended - EPollPoller.cc:65
20131108 09:38:46.891599Z 7557 TRACE printActiveChannels {8: IN } - EventLoop.cc:257
20131108 09:38:46.891611Z 7557 TRACE handleEvent [6] usecount=2 - Channel.cc:67
onMessage(): received 6 bytes from connection [TestServer:0.0.0.0:8888#1]
20131108 09:38:46.891744Z 7557 TRACE handleEvent [12] usecount=2 - Channel.cc:69
20131108 09:38:56.901306Z 7557 TRACE poll nothing happended - EPollPoller.cc:74

可以看到，fd = 6 是监听套接字，fd = 8是返回来的已连接套接字，那么fd = 7去哪了呢？其实是被acceptor的 idleFd_ 占据了。

连接建立的时候回调onConnection()，我们在telnet 上输入aaaa，服务器端消息到来，fd=8可读事件发生，回调onMessage()，加上\r\n 所以收到6个字节数据。

参考：

《UNP》

muduo manual.pdf

《linux 多线程服务器编程：使用muduo c++网络库》

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