SrsConnection* conn = NULL;
    if (type == SrsListenerRtmpStream) {
        conn = new SrsRtmpConn(this, client_stfd);
    } else if (type == SrsListenerHttpApi) {
#ifdef SRS_AUTO_HTTP_API
        conn = new SrsHttpApi(this, client_stfd, http_api_mux);
#else
        srs_warn("close http client for server not support http-api");
        srs_close_stfd(client_stfd);
        return ret;
#endif
    } else if (type == SrsListenerHttpStream) {
#ifdef SRS_AUTO_HTTP_SERVER
        conn = new SrsResponseOnlyHttpConn(this, client_stfd, http_server);
#else
        srs_warn("close http client for server not support http-server");
        srs_close_stfd(client_stfd);
        return ret;
#endif
    } else {
        // TODO: FIXME: handler others
    }
    srs_assert(conn);

/**
 * the manager for connection.
 * SrsServer类实现了这一接口,用来对SrsConnection类进行管理.
 */
class IConnectionManager
{
public:
    IConnectionManager();
    virtual ~IConnectionManager();
public:
    /**
     * remove the specified connection.
     */
    virtual void remove(SrsConnection* c) = 0;
};

/**
* the basic connection of SRS,
* all connections accept from listener must extends from this base class,
* server will add the connection to manager, and delete it when remove.
*/
class SrsConnection : public virtual ISrsOneCycleThreadHandler, public virtual IKbpsDelta
{
private:
    /**
    * each connection start a green thread,
    * when thread stop, the connection will be delete by server.
　　* 业务处理线程
    */
    SrsOneCycleThread* pthread;
    /**
    * the id of connection.
    */
    int id;
protected:
    /**
    * the manager object to manage the connection.
    */
    IConnectionManager* manager;
    /**
    * the underlayer st fd handler.
    */
    st_netfd_t stfd;
    /**
    * the ip of client.
    */
    std::string ip;
    /**
     * whether the connection is disposed,
     * when disposed, connection should stop cycle and cleanup itself.
     */
    bool disposed;
    /**
     * whether connection is expired, application definition.
     * when expired, the connection must never be served and quit ASAP.
     */
    bool expired;
public:
    SrsConnection(IConnectionManager* cm, st_netfd_t c);
    virtual ~SrsConnection();
public:
    /**
     * to dipose the connection.
     */
    virtual void dispose();
    /**
    * start the client green thread.
    * when server get a client from listener, 
    * 1. server will create an concrete connection(for instance, RTMP connection),
    * 2. then add connection to its connection manager,
    * 3. start the client thread by invoke this start()
    * when client cycle thread stop, invoke the on_thread_stop(), which will use server
    * to remove the client by server->remove(this).
    */
    virtual int start();
// interface ISrsOneCycleThreadHandler
public:
    /**
    * the thread cycle function,
    * when serve connection completed, terminate the loop which will terminate the thread,
    * thread will invoke the on_thread_stop() when it terminated.
    */
    virtual int cycle();
    /**
    * when the thread cycle finished, thread will invoke the on_thread_stop(),
    * which will remove self from server, server will remove the connection from manager 
    * then delete the connection.
    */
    virtual void on_thread_stop();
public:
    /**
    * get the srs id which identify the client.
    */
    virtual int srs_id();
    /**
     * set connection to expired.
     */
    virtual void expire();
protected:
    /**
    * for concrete connection to do the cycle.
　　* 具体connection 的处理函数,参见SrsRtmpConn.
    */
    virtual int do_cycle() = 0;
};

int SrsConnection::start()
{
　　// 启动SrsOneCycleThread类
    return pthread->start();
}

int SrsConnection::cycle()
{
    int ret = ERROR_SUCCESS;
    //这是个全局的id生成器,也用来生成st thread的id
    _srs_context->generate_id();
    id = _srs_context->get_id();
    // 取得客户端的ip地址
    ip = srs_get_peer_ip(st_netfd_fileno(stfd));
    // 调用子类如SrsRtmpConn的处理函数
    ret = do_cycle();
    
    // if socket io error, set to closed.
    if (srs_is_client_gracefully_close(ret)) {
        ret = ERROR_SOCKET_CLOSED;
    }
    
    // success.
    if (ret == ERROR_SUCCESS) {
        srs_trace("client finished.");
    }
    
    // client close peer.
    if (ret == ERROR_SOCKET_CLOSED) {
        srs_warn("client disconnect peer. ret=%d", ret);
    }

    return ERROR_SUCCESS;
}

void SrsConnection::on_thread_stop()
{
    // TODO: FIXME: never remove itself, use isolate thread to do cleanup.
　　// 用在SrsServer类的conns向量数组中删除此对象
　　 manager->remove(this);
}

int SrsConnection::srs_id()
{
    return id;
}

void SrsConnection::expire()
{
    expired = true;
}

SrsRtmpConn::SrsRtmpConn(SrsServer* svr, st_netfd_t c)
    : SrsConnection(svr, c)
{
    server = svr;
    req = new SrsRequest();
    res = new SrsResponse();
    skt = new SrsStSocket(c);//实现ISrsProtocolReaderWriter接口,即st socket的读写函数,以及读写超时,发送和接受到的字节数
    rtmp = new SrsRtmpServer(skt);// 提供rtmp-command-protocol服务,是一个上层的面向协议,media stream的服务,
// 例如连接vhost/app,播放流,获取视频/音频数据,与之对应的是 SrsRtmpClient.

    refer = new SrsRefer();
    bandwidth = new SrsBandwidth();
    security = new SrsSecurity();
    duration = 0;
    kbps = new SrsKbps();
    kbps->set_io(skt, skt);
    wakable = NULL;
    
    mw_sleep = SRS_PERF_MW_SLEEP;
    mw_enabled = false;
    realtime = SRS_PERF_MIN_LATENCY_ENABLED;
    send_min_interval = 0;
    tcp_nodelay = false;
    client_type = SrsRtmpConnUnknown;
    // 在配置改变时,支持reload
    _srs_config->subscribe(this);
}

// TODO: return detail message when error for client.
int SrsRtmpConn::do_cycle()
{
    int ret = ERROR_SUCCESS;
    
    srs_trace("RTMP client ip=%s", ip.c_str());

// 设置SrsRtmpServer里面的底层数据通讯类SrsProtocol的读写超时
    rtmp->set_recv_timeout(SRS_CONSTS_RTMP_RECV_TIMEOUT_US);
    rtmp->set_send_timeout(SRS_CONSTS_RTMP_SEND_TIMEOUT_US);
    // 握手
    if ((ret = rtmp->handshake()) != ERROR_SUCCESS) {
        srs_error("rtmp handshake failed. ret=%d", ret);
        return ret;
    }
    srs_verbose("rtmp handshake success");
    // 获取连接的app
    if ((ret = rtmp->connect_app(req)) != ERROR_SUCCESS) {
        srs_error("rtmp connect vhost/app failed. ret=%d", ret);
        return ret;
    }
    srs_verbose("rtmp connect app success");
    
    // set client ip to request.
    req->ip = ip;
    // 假设推流地址 rtmp://192.168.151.151/live/marstv
    // discovery vhost, resolve the vhost from config
　　req->vhost 是192.168.151.151

    SrsConfDirective* parsed_vhost = _srs_config->get_vhost(req->vhost);
// 没有设置 192.168.151.151 这样的vhost parsed_vhost是默认的vhost
    if (parsed_vhost) {
        req->vhost = parsed_vhost->arg0();// req->vhost 是 __defaultVhost__
    }
    
    srs_info("discovery app success. schema=%s, vhost=%s, port=%s, app=%s",
        req->schema.c_str(), req->vhost.c_str(), req->port.c_str(), req->app.c_str());
    
    if (req->schema.empty() || req->vhost.empty() || req->port.empty() || req->app.empty()) {
        ret = ERROR_RTMP_REQ_TCURL;
        srs_error("discovery tcUrl failed. "
            "tcUrl=%s, schema=%s, vhost=%s, port=%s, app=%s, ret=%d",
            req->tcUrl.c_str(), req->schema.c_str(), req->vhost.c_str(), req->port.c_str(), req->app.c_str(), ret);
        return ret;
    }
    
    // check vhost

// 在 check_vhost里面会调用 http_hooks_on_connect
    if ((ret = check_vhost()) != ERROR_SUCCESS) {
        srs_error("check vhost failed. ret=%d", ret);
        return ret;
    }
    srs_verbose("check vhost success.");
    
    srs_trace("connect app, "
        "tcUrl=%s, pageUrl=%s, swfUrl=%s, schema=%s, vhost=%s, port=%s, app=%s, args=%s", 
        req->tcUrl.c_str(), req->pageUrl.c_str(), req->swfUrl.c_str(), 
        req->schema.c_str(), req->vhost.c_str(), req->port.c_str(),
        req->app.c_str(), (req->args? "(obj)":"null"));
    
    // show client identity
    if(req->args) {
        std::string srs_version;
        std::string srs_server_ip;
        int srs_pid = 0;
        int srs_id = 0;
        
        SrsAmf0Any* prop = NULL;
        if ((prop = req->args->ensure_property_string("srs_version")) != NULL) {
            srs_version = prop->to_str();
        }
        if ((prop = req->args->ensure_property_string("srs_server_ip")) != NULL) {
            srs_server_ip = prop->to_str();
        }
        if ((prop = req->args->ensure_property_number("srs_pid")) != NULL) {
            srs_pid = (int)prop->to_number();
        }
        if ((prop = req->args->ensure_property_number("srs_id")) != NULL) {
            srs_id = (int)prop->to_number();
        }
        
        srs_info("edge-srs ip=%s, version=%s, pid=%d, id=%d", 
            srs_server_ip.c_str(), srs_version.c_str(), srs_pid, srs_id);
        if (srs_pid > 0) {
            srs_trace("edge-srs ip=%s, version=%s, pid=%d, id=%d", 
                srs_server_ip.c_str(), srs_version.c_str(), srs_pid, srs_id);
        }
    }
    
    ret = service_cycle();
    
    http_hooks_on_close();

    return ret;
}