muduo源码分析：TcpServer类
上篇博文学习了Acceptor class 的实现，它仅仅是对Channel和Socket的简单封装，对使用者来说简单易用。这得益于底层架构Reactor。接下来，开始学习muduo对于建立连接的处理。这属于muduo提到的三个半事件中的第一个。可以想一下，TcpServer class应该也是对Acceptor，Poller的封装。
连接处理过程
首先TcpServer通过Acceptor向Poller注册了一个Channel，该Channel关注acceptSocket的readable事件，并设置了回调函数Acceptor::newConnectionCallback 为 TcpServer::newConnection 。
acceptor_->setNewConnectionCallback(boost::bind(&TcpServer::newConnection, this, _1, _2)); //绑定Acceptor::newConnectionCallback回调函数然后，当有client连接时，Poller返回该Channel，接着调用该Channel::handleEvent–>handleRead。在Acceptor中accept该连接，然后调用设置好的 Acceptor::newConnectionCallback ,即 TcpServer::newConnection 。
接着，对于每个连接，TcpServer会创建一个TcpConnnection来管理。TcpConnection是最为复杂的一个class，使用shared_ptr管理，因为它的生命周期比较模糊，这一点后面再分析。
最后，会调用TcpConnnection::connectEstablish,它会回调用户设置好的回调函数 connectionCallback。
（类与类之间通过回调函数联系在了一起）
TcpServer.h
class TcpServer : boost::noncopyable
{
public:
typedef boost::function ThreadInitCallback;
enum Option
{
kNoReusePort,
kReusePort,
};
//TcpServer(EventLoop* loop, const InetAddress& listenAddr);
TcpServer(EventLoop* loop, //构造函数
const InetAddress& listenAddr,
const string& nameArg,
Option option = kNoReusePort);
~TcpServer(); // force out-line dtor, for scoped_ptr members.
const string& ipPort() const { return ipPort_; }
const string& name() const { return name_; }
EventLoop* getLoop() const { return loop_; }
void setThreadNum(int numThreads); //设置server中需要运行多少个Loop线程
void setThreadInitCallback(const ThreadInitCallback& cb)
{ threadInitCallback_ = cb; }
/// valid after calling start()
boost::shared_ptr threadPool()
{ return threadPool_; }
void start(); //启动该TcpServer架构
void setConnectionCallback(const ConnectionCallback& cb) //设置新连接回调
{ connectionCallback_ = cb; }
void setMessageCallback(const MessageCallback& cb) //设置消息回调
{ messageCallback_ = cb; }
void setWriteCompleteCallback(const WriteCompleteCallback& cb) //设置写完成回调
{ writeCompleteCallback_ = cb; }
private:
void newConnection(int sockfd, const InetAddress& peerAddr); //被设置为Acceptor::newConnectionCallback()回调函数
void removeConnection(const TcpConnectionPtr& conn);
void removeConnectionInLoop(const TcpConnectionPtr& conn);
typedef std::map ConnectionMap; //使用map关联容器维护一个连接列表
EventLoop* loop_; // the acceptor loop
const string ipPort_; //端口号
const string name_; //名字
boost::scoped_ptr acceptor_; //用于接受连接的Acceptor
boost::shared_ptr threadPool_;
ConnectionCallback connectionCallback_; //新连接回调
MessageCallback messageCallback_; //消息回调
WriteCompleteCallback writeCompleteCallback_; //写完成回调
ThreadInitCallback threadInitCallback_;
AtomicInt32 started_; //启动标记
// always in loop thread
int nextConnId_; //下一个连接ID
ConnectionMap connections_; //连接列表
}; 几个重要成员：
boost::scoped_ptr
EventLoop* loop_; Reactor的关键class
map
TcpServer::TcpServer()
TcpServer::TcpServer(EventLoop* loop,
const InetAddress& listenAddr,
const string& nameArg,
Option option)
: loop_(CHECK_NOTNULL(loop)),
ipPort_(listenAddr.toIpPort()),
name_(nameArg),
acceptor_(new Acceptor(loop, listenAddr, option == kReusePort)),
threadPool_(new EventLoopThreadPool(loop, name_)),
connectionCallback_(defaultConnectionCallback),
messageCallback_(defaultMessageCallback),
nextConnId_(1)
{
acceptor_->setNewConnectionCallback(boost::bind(&TcpServer::newConnection, this, _1, _2)); //绑定newConnectionCallback回调函数
}
TcpServer::~TcpServer()
TcpServer::~TcpServer()
{
loop_->assertInLoopThread();
LOG_TRACE << "TcpServer::~TcpServer [" << name_ << "] destructing";
for (ConnectionMap::iterator it(connections_.begin());
it != connections_.end(); ++it)
{
TcpConnectionPtr conn(it->second);
it->second.reset();
conn->getLoop()->runInLoop(
boost::bind(&TcpConnection::connectDestroyed, conn));
}
}
TcpServer::newConnection
void TcpServer::newConnection(int sockfd, const InetAddress& peerAddr) //新连接处理函数
{
loop_->assertInLoopThread();
EventLoop* ioLoop = threadPool_->getNextLoop(); //轮询调用线程池的EventLoop循环
char buf[64];
snprintf(buf, sizeof buf, "-%s#%d", ipPort_.c_str(), nextConnId_); //生成唯一的name
++nextConnId_;i //++之后就是下一个连接id
string connName = name_ + buf;
LOG_INFO << "TcpServer::newConnection [" << name_
<< "] - new connection [" << connName
<< "] from " << peerAddr.toIpPort();
InetAddress localAddr(sockets::getLocalAddr(sockfd)); //构造本地地址
// FIXME poll with zero timeout to double confirm the new connection
// FIXME use make_shared if necessary
TcpConnectionPtr conn(new TcpConnection(ioLoop, connName, sockfd, localAddr, peerAddr)); //构造新的TcpConnection,将获取的EventLoop的地址传给新连接对象。
connections_[connName] = conn; //将该TcpConnection加入到TcpServer的map容器中
//设置TcpConnection三个半事件回调函数，将用户给TcpServer设置的回调传递给TCPConnection
conn->setConnectionCallback(connectionCallback_);
conn->setMessageCallback(messageCallback_);
conn->setWriteCompleteCallback(writeCompleteCallback_);
conn->setCloseCallback(
boost::bind(&TcpServer::removeConnection, this, _1)); // FIXME: unsafe
//调用conn->connectEstablished()
ioLoop->runInLoop(boost::bind(&TcpConnection::connectEstablished, conn));
}TcpServer::removeConnection()
void TcpServer::removeConnection(const TcpConnectionPtr& conn)
{
// FIXME: unsafe
loop_->runInLoop(boost::bind(&TcpServer::removeConnectionInLoop, this, conn));
}
void TcpServer::removeConnectionInLoop(const TcpConnectionPtr& conn)
{
loop_->assertInLoopThread();
LOG_INFO << "TcpServer::removeConnectionInLoop [" << name_
<< "] - connection " << conn->name();
size_t n = connections_.erase(conn->name()); //将该TcpConnection从map容器中删除
(void)n;
assert(n == 1);
EventLoop* ioLoop = conn->getLoop();
ioLoop->queueInLoop(
boost::bind(&TcpConnection::connectDestroyed, conn));
}
使用示例
void onConnection(const muduo::net::TcpConnectionPtr& conn)
{
if(conn->connected()) {
std::cout << "New connection" << std::endl;
} else {
std::cout << "Connection failed" << std::endl;
}
}
void onMessage(const muduo::net::TcpConnectionPtr& conn,
muduo::net::Buffer *buffer)
//const char* data,
//ssize_t len)
{
const std::string readbuf = buffer->retrieveAllAsString();
std::cout << "Receive :" << readbuf.size()<< " bytes." << std::endl
<< "Content:" << readbuf << std::endl;
}
int main()
{
muduo::net::EventLoop loop;
muduo::net::TcpServer server(&loop, "8090");
server.setConnectionCallback(onConnection);
server.setMessageCallback(onMessage);
server.start();
loop.loop();
}可以看到TcpServer使用比较方便，只需要设置好相应的回调函数，然后start()。
TcpServer在后台默默地做了很多事情：socket、bind、listen、epoll_wait、accept等等。