.net异步套接字超时检查线程安全

Question

http://msdn.microsoft.com/en-us /library/system.net.sockets.socketasynceventargs.aspx

从上面的 msdn 示例开始，我尝试编写一个超时检查，它将关闭不活动的客户端套接字并释放资源。

这就是我想出的办法。 但我不确定它是否完全线程安全以及是否有更好的方法来做到这一点。 我希望有人能给一些建议。

void IO_Completed(object sender, SocketAsyncEventArgs e)
{
    if (e.SocketError != SocketError.Success)
    {
        CloseClientSocket(e);
        return;
    }

    if (1 < Interlocked.CompareExchange(ref token.Status, 1, 0))
        return;

    switch (e.LastOperation)
    {
        case SocketAsyncOperation.Receive:
            ProcessReceive(e);
            break;
        ...
    }

    token.LastActive = Environment.TickCount;
    Interlocked.CompareExchange(ref token.Status, 0, 1);
}

void ProcessReceive(SocketAsyncEventArgs e)
{
    AsyncUserToken token = (AsyncUserToken)e.UserToken;
    if (e.BytesTransferred > 0)
        if (!token.Socket.SendAsync(e))
            ProcessSend(e);
    else
        CloseClientSocket(e);
}

void ProcessSend(SocketAsyncEventArgs e)
{
    AsyncUserToken token = (AsyncUserToken)e.UserToken;
    if (!token.Socket.ReceiveAsync(e))
        ProcessReceive(e);
}

TimeoutCheck 将每 20 秒执行一次。 allReadWriteArgs 是一个包含所有 SocketAsyncEventArgs 的数组。 关闭套接字后，将通过 SocketError.OperationAborted 调用 IO_Completed。

void TimeoutCheck(object state)
{
    AsyncUserToken token;
    int timeout = Environment.TickCount - 20000;
    for (int i = 0; i < allReadWriteArgs.Length; i++)
    {
        token = (AsyncUserToken)allReadWriteArgs[i].UserToken;
        if (token.LastActive < timeout)
            if (0 == Interlocked.CompareExchange(ref token.Status, 2, 0))
                Interlocked.Exchange(ref token.Socket, null).Close();
    }
}


void CloseClientSocket(SocketAsyncEventArgs e)
{
    AsyncUserToken token = e.UserToken as AsyncUserToken;

    if (token.Socket != null)
    {
        try
        {
            token.Socket.Shutdown(SocketShutdown.Both);
        }
        catch (SocketException) { }
        token.Socket.Close();
    }

    token.Status = 2;
    bufferManager.FreeBuffer(e);
    readWritePool.Push(e);
    ...
}

Answer 1

你的代码看起来不错。 你也可以做这样的事情：

void _connectionActivityCheck_Elapsed(object sender, System.Timers.ElapsedEventArgs e)
{
    _connectionActivityCheck.Stop();

    try
    {
        List<Guid> connectionsToRemove = new List<Guid>();

        lock (_connections.SyncRoot)
        {
            IncomingConnection conn;

            foreach (DictionaryEntry item in _connections)
            {
                conn = (IncomingConnection)item.Value;

                if (conn.LastIncomingActivity.HasValue && 
                    DateTime.Now.Subtract(conn.LastIncomingActivity.Value).TotalSeconds > MaximumInactivitySeconds)
                        connectionsToRemove.Add(conn.ConnectionId);
            }
        }

        if (connectionsToRemove.Count > 0)
        {
            int itemsToRemove = connectionsToRemove.Count;

            foreach (Guid item in connectionsToRemove)
            {
                RemoveConnection(item);
            }

            Context.Current.Logger.LogInfo(_loggerName, 
                string.Format("{0} connections were closed due to incoming traffic inactivity", itemsToRemove));
        }
    }
    catch (Exception ex)
    {
        Context.Current.Logger.LogFatal(_loggerName, "An error ocurred while checking incoming traffic.", ex);
    }
    finally
    {
        _connectionActivityCheck.Start();
    }
}



private void RemoveConnection(Guid connectionId)
{
    lock (_connections.SyncRoot)
    {
        try
        {
            IncomingConnection conn = _connections[connectionId] as IncomingConnection;

            if (conn != null)
            {
                try
                {
                    conn.Dispose();
                }
                catch { }

                _connections.Remove(connectionId);
            }
        }
        catch { }
    }
}