QTcpSocket 保持活动选项不起作用

Question

我有一个简单的程序作为我的客户端，包含一个 tcp 套接字 (QTcpSocket)。我的客户代码如下：

while (tcpSocket.data()->waitForConnected(maxWaitingTimeToConnect) == false)
{
    tcpSocket.data()->connectToHost(serverIP, serverPort);
    if (maxRetryNumberToConnect != -1 && retryNumber++ > maxRetryNumberToConnect)
    {
        qDebug() << "Socket is disconnected and maximum try for re-connection reached.";
        return false;
    }
    emit sgl_tryToConnect();
    // Socket is disconnected and trying to re-connect
    QThread::msleep(100);
}
qDebug() << "Client is connected";
qDebug() << tcpSocket.data()->localPort();
auto sd = tcpSocket.data()->socketDescriptor();
NetworkShared::setSocketOption(&sd);

下面还给出了哪个setSocketOption：

/// Set keepAlive
int enableKeepAlive = 1;
/* Set socket FD's option OPTNAME at protocol level LEVEL
   to *OPTVAL (which is OPTLEN bytes long).
   Returns 0 on success, -1 for errors.  */
qDebug() << setsockopt(*socketDescriptor, SOL_SOCKET, SO_KEEPALIVE, &enableKeepAlive, sizeof(enableKeepAlive));

int maxIdle = 1; /// Seconds
qDebug() << setsockopt(*socketDescriptor, SOL_TCP, TCP_KEEPIDLE, &maxIdle, sizeof(maxIdle));

int count = 1;  /// Send up to 1 keepalive packets out, then disconnect if no response
qDebug() << setsockopt(*socketDescriptor, SOL_TCP, TCP_KEEPCNT, &count, sizeof(count));

int interval = 1;  /// Send a keepalive packet out every 1 seconds (after the 1 second idle period)
qDebug() << setsockopt(*socketDescriptor, SOL_TCP, TCP_KEEPINTVL, &interval, sizeof(interval));

当我运行我的程序时，一切看起来都很好，并且将为我的套接字启用 keepalive 选项。但是当我在客户端拔下电缆时它不起作用。我将我的 netstat 输出带到下面，表明我的套接字启用了保活计时器。

tcp        0      0 192.168.2.157:37281     192.168.2.163:4444      ESTABLISHED keepalive (0.16/0/0)

我也像客户端一样在服务器端启用了 keepalive 选项。现在我有一些问题； 1- 我什么时候应该启用 keepalive 选项？连接到服务器之后还是连接之前？ 2- 我是否应该编写一些代码来捕获程序中的保活错误？

顺便说一下，我的程序是运行ning 在 linux mint 17.1 中，我还更改了 sysctl.conf 和 proc/sys 中的 keeplalive 选项，但没有用。

在此先感谢您的帮助。礼萨

Answer 1

最好用Qt的函数setSocketOption:

your_socket->setSocketOption(QAbstractSocket::KeepAliveOption, 1);

enum QAbstractSocket::SocketOption

This enum represents the options that can be set on a socket. If desired, they can be set after having received the connected() signal from the socket or after having received a new socket from a QTcpServer.

Note: On Windows Runtime, QAbstractSocket::KeepAliveOption must be set before the socket is connected.

并捕获任何连接错误：

connect (your_socket, static_cast<void (QTcpSocket::*)(QAbstractSocket::SocketError)>(&QAbstractSocket::error), this, &YourClass::onError);
// ...

void YourClass::onError(QAbstractSocket::SocketError socketError)
{
    switch(socketError)
    {
        case QAbstractSocket::ConnectionRefusedError:
        // ...
        // ...
    }
}

QTcpSocket 保持活动选项不起作用

QTcpSocket Keep alive option does not work

sockets

keep-alive

linux-mint

qtcpsocket