如何检测套接字C#断开连接? [英] How to detect a disconnected socket C#?

问题描述

我一直在使用C#编写套接字客户端程序，并且想知道如何检测套接字的另一端何时不正常地"断开自身的连接，例如在拔出网络电缆或进行硬重置时.

I've been working on a socket client program in C# and am wondering how to detect when the other end of a socket has disconnected itself "ungracefully" as in a network cable being unplugged or a hard reset.

我下面有这些功能来访问套接字，并根据SO问题 MSDN文章，检查套接字是否断开连接的最佳方法是发送长度为0的1字节消息.如果引发异常并且WSAEWOULDBLOCK不是错误代码，则插座已断开连接.我已经尝试过了，但是在硬重置服务器连接后，客户端将调用 Send(new byte [1]，0，0，SocketFlags.None)并成功返回，而 Receive()命令此后立即返回WSAEWOULDBLOCK错误.

I have these functions below to access the socket and according to the SO question here and this MSDN article, the best way to check for a disconnected socket is to send a 1-byte message with a length of 0. If an exception is thrown and WSAEWOULDBLOCK is not the error code then the socket is disconnected. I have tried this but after hard reseting the server connection the client will call Send(new byte[1], 0, 0, SocketFlags.None) and return successfully and the Receive() command right afterwards returns the WSAEWOULDBLOCK error.

有什么作用?

这是下面的代码. _socket 设置为非阻止模式:

Here's my code below. _socket is set to non-blocking mode:

private int nonBlockRecv(byte[] recvBytes, int offset, int size, SocketFlags sf)
{
    int bytesRecv = 0;

    while (true)
    {
        try
        {
            nonBlockSend(new byte[1], 0, 0, sf);
            bytesRecv = _socket.Receive(recvBytes, offset, size, sf);
            break;
        }
        catch (SocketException excp)
        {
            if (excp.ErrorCode != 10035) // WSAEWOULDBLOCK
                throw excp;
        }
    }

    return bytesRecv;
}

private int nonBlockSend(byte[] sendBytes, int offset, int size, SocketFlags sf)
{
    int bytesSent = 0;

    while (true)
    {
        try
        {
            _socket.Send(sendBytes, offset, size, sf);
            break;
        }
        catch (SocketException excp)
        {
            if (excp.ErrorCode != 10035) // WSAEWOULDBLOCK
                throw excp;
        }
    }

    return bytesSent;
}

这可能是有好处的，但是服务器是Windows Mobile设备.我在另一个线程中读到，不同的操作系统可能快要死了，就可以发送套接字关闭信号.也许Windows Mobile OS不会这样做?

This may be beneficial but the server is Windows Mobile device. I read in another thread that different OSs maybe able to send socket close signals when they're dying. Perhaps the Windows Mobile OS does not do this??

推荐答案

如果远程计算机正常断开会话连接，则 Socket.Receive()方法将返回0个字节.您必须检测到知道远端已断开连接:

If the remote computer gracefully disconnects the session, the Socket.Receive() method will return with 0 bytes. You must detect that to know that the remote end has disconnected:

int recv = sock.Receive(data);
if (recv == 0)
{
    // Remote client has disconnected.
}
else
{
    // Remote client has sent data.
}

此外，即使出现 SocketException ，您也可以标识套接字断开连接的异常.

Also, even if there SocketException arises you can identify the exception for socket disconnection.

希望这有助于解决您的问题.

Hope this helps solve your problem.

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