是否有可能检测客户端是否已关闭Stream?
情况简介:
我有一个服务,通过套接字发送回复信息。 连接不安全。 我想要设置另一项可以为这些连接提供TLS的服务 - 这项新服务将提供一个端口并根据提供的客户端证书分配连接。 我不想使用stunnel出于几个原因,其中之一就是每个接收端口需要一个转发端口。
我目前试图实现的解决方案:
本质上,我试图将一个SslStream(传入)与一个NetworkStream耦合(传出 - 可以是一个Socket,但是我将它放入一个NetworkStream中以匹配传入),并且具有读/写操作。 此链接将提供客户端(通过SSL / TLS)和服务(通过不安全的连接)之间的流程。
以下是我想出的链接这些流的类:
public class StreamConnector
{
public StreamConnector(Stream s1, Stream s2)
{
StreamConnectorState state1 = new StreamConnectorState(s1, s2);
StreamConnectorState state2 = new StreamConnectorState(s2, s1);
s1.BeginRead(state1.Buffer, 0, state1.Buffer.Length, new AsyncCallback(ReadCallback), state1);
s2.BeginRead(state2.Buffer, 0, state2.Buffer.Length, new AsyncCallback(ReadCallback), state2);
}
private void ReadCallback(IAsyncResult result)
{
// Get state object.
StreamConnectorState state = (StreamConnectorState)result.AsyncState;
// Finish reading data.
int length = state.InStream.EndRead(result);
// Write data.
state.OutStream.Write(state.Buffer, 0, length);
// Wait for new data.
state.InStream.BeginRead(state.Buffer, 0, state.Buffer.Length, new AsyncCallback(ReadCallback), state);
}
}
public class StreamConnectorState
{
private const int BYTE_ARRAY_SIZE = 4096;
public byte[] Buffer { get; set; }
public Stream InStream { get; set; }
public Stream OutStream { get; set; }
public StreamConnectorState(Stream inStream, Stream outStream)
{
Buffer = new byte[BYTE_ARRAY_SIZE];
InStream = inStream;
OutStream = outStream;
}
}
问题:
当客户端完成发送信息并处理SslStream时,服务器没有任何指示是否发生了这种情况。 这StreamConnector类愉快地继续运行到永恒,没有抛出任何错误,我找不到任何指标,它应该停止。 (当然,事实上,我每次在ReadCallback中得到0的长度,但是我需要能够提供长时间运行的连接,所以这不是一个很好的判断方法。)
另一个潜在的问题是即使没有数据可用,ReadCallback也会被调用。 如果我直接使用Socket而不是流,那么不确定这是否会有所不同,但保持一遍又一遍地运行该代码似乎效率低下。
我的问题:
1)有没有方法可以判断Stream是否从客户端被关闭?
2)有没有更好的方法去做我想做的事情?
2a)是否有更有效的方式来运行异步读/写循环?
编辑:谢谢,罗伯特。 原因是我没有关闭Streams(因为不知道如何判断Streams何时需要关闭),因此循环不断被调用。 我将包含完整的代码解决方案以防其他人遇到此问题:
/// <summary>
/// Connects the read/write operations of two provided streams
/// so long as both of the streams remain open.
/// Disposes of both streams when either of them disconnect.
/// </summary>
public class StreamConnector
{
public StreamConnector(Stream s1, Stream s2)
{
StreamConnectorState state1 = new StreamConnectorState(s1, s2);
StreamConnectorState state2 = new StreamConnectorState(s2, s1);
s1.BeginRead(state1.Buffer, 0, state1.Buffer.Length, new AsyncCallback(ReadCallback), state1);
s2.BeginRead(state2.Buffer, 0, state2.Buffer.Length, new AsyncCallback(ReadCallback), state2);
}
private void ReadCallback(IAsyncResult result)
{
// Get state object.
StreamConnectorState state = (StreamConnectorState)result.AsyncState;
// Check to make sure Streams are still connected before processing.
if (state.InStream.IsConnected() && state.OutStream.IsConnected())
{
// Finish reading data.
int length = state.InStream.EndRead(result);
// Write data.
state.OutStream.Write(state.Buffer, 0, length);
// Wait for new data.
state.InStream.BeginRead(state.Buffer, 0, state.Buffer.Length, new AsyncCallback(ReadCallback), state);
}
else
{
// Dispose of both streams if either of them is no longer connected.
state.InStream.Dispose();
state.OutStream.Dispose();
}
}
}
public class StreamConnectorState
{
private const int BYTE_ARRAY_SIZE = 4096;
public byte[] Buffer { get; set; }
public Stream InStream { get; set; }
public Stream OutStream { get; set; }
public StreamConnectorState(Stream inStream, Stream outStream)
{
Buffer = new byte[BYTE_ARRAY_SIZE];
InStream = inStream;
OutStream = outStream;
}
}
public static class StreamExtensions
{
private static readonly byte[] POLLING_BYTE_ARRAY = new byte[0];
public static bool IsConnected(this Stream stream)
{
try
{
// Twice because the first time will return without issue but
// cause the Stream to become closed (if the Stream is actually
// closed.)
stream.Write(POLLING_BYTE_ARRAY, 0, POLLING_BYTE_ARRAY.Length);
stream.Write(POLLING_BYTE_ARRAY, 0, POLLING_BYTE_ARRAY.Length);
return true;
}
catch (ObjectDisposedException)
{
// Since we're disposing of both Streams at the same time, one
// of the streams will be checked after it is disposed.
return false;
}
catch (IOException)
{
// This will be thrown on the second stream.Write when the Stream
// is closed on the client side.
return false;
}
}
}
您必须尝试读取或写入套接字 - 或基于它的任何东西 - 来检测断开连接。
试图写入会抛出一个异常/返回一个错误(取决于你的语言的范例),或者可能只写0字节。 试图读取将会抛出一个异常/返回一个错误(再次取决于你的语言的范例)或返回null
。
值得注意的是,如果您使用的是基于select的服务器模型,那么断开连接的套接字会在断开连接时显示 - 即返回select - 可读,然后尝试从中读取并获取错误或null
。
我忍不住想你的客户应该告诉服务器何时完成某种消息。 最好准备一个电线被切断或电源故障或拔出一个插头,但通常你想用某种类型的信息结束标记来终止连接。 保存真正问题的例外,而不是正常的会话。
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