//on 是 1 表示打开 keepalive 选项，为 0 表示关闭，0 是默认值
int on = 1;
setsockopt(fd, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof(on));

//发送 keepalive 报文的时间间隔
int val = 7200;
setsockopt(fd, IPPROTO_TCP, TCP_KEEPIDLE, &val, sizeof(val));

//两次重试报文的时间间隔
int interval = 75;
setsockopt(fd, IPPROTO_TCP, TCP_KEEPINTVL, &interval, sizeof(interval));

int cnt = 9;
setsockopt(fd, IPPROTO_TCP, TCP_KEEPCNT, &cnt, sizeof(cnt));

[root@iZ238vnojlyZ ~]# sysctl -a | grep keepalive
net.ipv4.tcp_keepalive_intvl = 75
net.ipv4.tcp_keepalive_probes = 9
net.ipv4.tcp_keepalive_time = 7200

//开启 keepalive 选项
const char on = 1;
setsockopt(socket, SOL_SOCKET, SO_KEEPALIVE, (char *)&on, sizeof(on);

// 设置超时详细信息
DWORD cbBytesReturned;
tcp_keepalive klive;
// 启用保活
klive.onoff = 1;
klive.keepalivetime = 7200;
// 重试间隔为10秒
klive.keepaliveinterval = 1000 * 10; 
WSAIoctl(socket, SIO_KEEPALIVE_VALS, &klive, sizeof(tcp_keepalive), NULL, 0, &cbBytesReturned, NULL, NULL);

bool CIUSocket::Send()
{
    int nSentBytes = 0;
    int nRet = 0;
    while (true)
    {
        nRet = ::send(m_hSocket, m_strSendBuf.c_str(), m_strSendBuf.length(), 0);
        if (nRet == SOCKET_ERROR)
        {
            if (::WSAGetLastError() == WSAEWOULDBLOCK)
                break;
            else
            {
                LOG_ERROR("Send data error, disconnect server:%s, port:%d.", m_strServer.c_str(), m_nPort);
                Close();
                return false;
            }
        }
        else if (nRet < 1)
        {
            //一旦出现错误就立刻关闭Socket
            LOG_ERROR("Send data error, disconnect server:%s, port:%d.", m_strServer.c_str(), m_nPort);
            Close();
            return false;
        }

        m_strSendBuf.erase(0, nRet);
        if (m_strSendBuf.empty())
            break;

        ::Sleep(1);
    }

    {
        //记录一下最近一次发包时间
        std::lock_guard<std::mutex> guard(m_mutexLastDataTime);
        m_nLastDataTime = (long)time(NULL);
    }

    return true;
}


bool CIUSocket::Recv()
{
    int nRet = 0;
    char buff[10 * 1024];
    while (true)
    {

        nRet = ::recv(m_hSocket, buff, 10 * 1024, 0);
        if (nRet == SOCKET_ERROR)                //一旦出现错误就立刻关闭Socket
        {
            if (::WSAGetLastError() == WSAEWOULDBLOCK)
                break;
            else
            {
                LOG_ERROR("Recv data error, errorNO=%d.", ::WSAGetLastError());
                //Close();
                return false;
            }
        }
        else if (nRet < 1)
        {
            LOG_ERROR("Recv data error, errorNO=%d.", ::WSAGetLastError());
            //Close();
            return false;
        }

        m_strRecvBuf.append(buff, nRet);

        ::Sleep(1);
    }

    {
        std::lock_guard<std::mutex> guard(m_mutexLastDataTime);
        //记录一下最近一次收包时间
        m_nLastDataTime = (long)time(NULL);
    }

    return true;
}

void CIUSocket::RecvThreadProc()
{
    LOG_INFO("Recv data thread start...");

    int nRet;
    //上网方式 
    DWORD   dwFlags;
    BOOL    bAlive;
    while (!m_bStop)
    {
        //检测到数据则收数据
        nRet = CheckReceivedData();
        //出错
        if (nRet == -1)
        {
            m_pRecvMsgThread->NotifyNetError();
        }
        //无数据
        else if (nRet == 0)
        {           
            long nLastDataTime = 0;
            {
                std::lock_guard<std::mutex> guard(m_mutexLastDataTime);
                nLastDataTime = m_nLastDataTime;
            }

            if (m_nHeartbeatInterval > 0)
            {
                //当前系统时间与上一次收发数据包的时间间隔超过了m_nHeartbeatInterval
                //则发一次心跳包
                if (time(NULL) - nLastDataTime >= m_nHeartbeatInterval)
                    SendHeartbeatPackage();
            }
        }
        //有数据
        else if (nRet == 1)
        {
            if (!Recv())
            {
                m_pRecvMsgThread->NotifyNetError();
                continue;
            }

            DecodePackages();
        }// end if
    }// end while-loop

    LOG_INFO("Recv data thread finish...");
}

void BusinessSession::send(const char* pData, int dataLength)
{
    bool sent = TcpSession::send(pData, dataLength);

    //发送完数据更新下发包时间
    updateHeartbeatTime();      
}
void BusinessSession::handlePackge(char* pMsg, int msgLength, bool& closeSession, std::vector<std::string>& vectorResponse)
{
    //对数据合法性进行校验
    if (pMsg == NULL || pMsg[0] == 0 || msgLength <= 0 || msgLength > MAX_DATA_LENGTH)
    {
        //非法刺探请求，不做任何应答，直接关闭连接
        closeSession = true;
        return;
    }

    //更新下收包时间
    updateHeartbeatTime();

    //省略包处理代码...
}

void BusinessSession::updateHeartbeatTime()
{
    std::lock_guard<std::mutex> scoped_guard(m_mutexForlastPackageTime);
    m_lastPackageTime = (int64_t)time(nullptr);
}

bool BusinessSession::doHeartbeatCheck()
{
    const Config& cfg = Singleton<Config>::Instance();
    int64_t now = (int64_t)time(nullptr);

    std::lock_guard<std::mutex> lock_guard(m_mutexForlastPackageTime);
    if (now - m_lastPackageTime >= cfg.m_nMaxClientDataInterval)
    {
        //心跳包检测，超时，关闭连接
        LOGE("heartbeat expired, close session");
        shutdown();
        return true;
    }

    return false;
}

void TcpServer::checkSessionHeartbeat()
{
    int64_t now = (int64_t)time(nullptr);
    if (now - m_nLastCheckHeartbeatTime >= m_nHeartbeatCheckInterval)
    {
        m_spSessionManager->checkSessionHeartbeat();
        m_nLastCheckHeartbeatTime = (int64_t)time(nullptr);
    }      
}

void SessionManager::checkSessionHeartbeat()
{   
    std::lock_guard<std::mutex> scoped_lock(m_mutexForSession);
    for (const auto& iter : m_mapSessions)
    {
        //这里调用 BusinessSession::doHeartbeatCheck()
        iter.second->doHeartbeatCheck();
    }  
}

ChatSession::ChatSession(const std::shared_ptr<TcpConnection>& conn, int sessionid) :
TcpSession(conn), 
m_id(sessionid),
m_seq(0),
m_isLogin(false)
{
    m_userinfo.userid = 0;
    m_lastPackageTime = time(NULL);

//这里设置了非调试模式下才开启心跳包检测功能
#ifndef _DEBUG
    EnableHearbeatCheck();
#endif
}

void BusinessSession::send(std::string_view strResponse)
{   
    bool success = WebSocketSession::send(strResponse);

    if (success)
    {
        bool enablePingPongLog = Singleton<Config>::Instance().m_bPingPongLogEnabled;

        //其他消息正常打印，心跳消息按需打印
        if (strResponse != "pong" || enablePingPongLog)
        {
            LOGI("msg sent to client [%s], sessionId: %s, session: 0x%0x, clientId: %s, accountId: %s, frontId: %s, msg: %s",
                 getClientInfo(), m_strSessionId.c_str(), (int64_t)this, m_strClientID.c_str(), m_strAccountID.c_str(), BusinessSession::m_strFrontId.c_str(), strResponse.data());
        }
    }
}