从封闭的NetworkStream读取不会引起任何异常 [英] Reading from closed NetworkStream doesn't cause any exception
问题描述
我试图创建一个相当简单的客户端 - 服务器应用程序，但对于通信我想使用二进制序列化对象。通信本身看起来相当不错，但是当我关闭客户端的侧流，服务器并没有真正注意到它，并不断尝试读取数据流。
I'm trying to create a rather simple client-server application, but for communication I want to use binary serialized objects. The communication itself seems rather fine, but when I close the stream on the client's side, the server doesn't really notice it and keeps on trying to read the stream.
服务器端（Server类，在不同的线程中执行）：
server side (class Server, executed in separate thread):
监听连接
listener = new TcpListener(IPAddress.Parse("127.0.0.1"), this.Port);
listener.Start();
while (!interrupted)
{
Console.WriteLine("Waiting for client");
TcpClient client = listener.AcceptTcpClient();
AddClient(client);
Console.WriteLine("Client connected");
}
添加客户端：
adding the client:
public void AddClient(TcpClient socket)
{
Client client = new Client(this, socket);
this.clients.Add(client);
client.Start();
}
听消息（深客户端类中）：
listening for messages (deep inside Client class):
BinaryFormatter deserializer = new BinaryFormatter();
while (!interrupted)
{
System.Diagnostics.Debug.WriteLine("Waiting for the message...");
AbstractMessage msg = (AbstractMessage)deserializer.Deserialize(stream);
System.Diagnostics.Debug.WriteLine("Message arrived: " + msg.GetType());
raiseEvent(msg);
}
单元测试：
unit test:
Server server = new Server(6666);
server.Start();
Thread.Sleep(500);
TcpClient client = new TcpClient("127.0.0.1", 6666);
var message = new IntroductionMessage();
byte[] arr = message.Serialize();
client.GetStream().Write(arr, 0, arr.Length);
Thread.Sleep(500);
Assert.AreEqual(1, server.Clients.Count);
client.GetStream().Close();
client.Close();
Thread.Sleep(1000);
Assert.AreEqual(0, server.Clients.Count);
server.Stop();
因此，该消息得到正确读取，但后来，当我关闭流，deserializer.Deserialize（流）似乎不抛出任何异常...所以应该只是无法读取这种方式，或者我应该关闭客户端以不同的方式？
so the message gets read properly, but then, when I close the stream, deserializer.Deserialize(stream) doesn't appear to throw any exceptions... so should it just not be read this way, or should I close the client in a different way?
推荐答案
假设服务器中使用的反序列化的信息流是的的NetworkStream （这是由 TcpClient.GetStream（）的返回流的类型），你应该做两件事情：
Assuming the stream used in the Server for deserializing the message is a NetworkStream (which is the type of the stream returned by TcpClient.GetStream()), you should do two things:
-
定义连接两端的具体消息。当服务器接收和反序列化此消息，退出while循环。为了使这项工作，客户显然需要关闭其TcpClient的连接之前发送这样的消息。 （您可以选择不同的机制以类似的方式工作 - 但为什么不使用消息机制，你已经在地方...）
Define a specific message for "connection ends". When the server receives and deserializes this message, exit the while-loop. To make this work, the client obviously needs to send such a message before closing its TcpClient connection. (You might choose a different mechanism working in a similar manner -- but why not using the message mechanism you already have in place...)
设置 ReadTimeout 上的的NetworkStream 的，所以在情况下，连接丢失，客户不能发送一个连接终止的消息时，服务器将达到超时，实现了客户端是死
Set a ReadTimeout on the NetworkStream, so in case the connection gets lost and the client is unable to send a "connection ends" message, the server will hit the timeout and realize that the client is "dead".
在你的服务器的代码，用于收听的客户端消息应类似于这样：
The code in your server for listening to client messages should look similar to this:
//
// Time-out after 1 minute after receiving last message
//
stream.ReadTimeOut = 60 * 1000;
BinaryFormatter deserializer = new BinaryFormatter();
try
{
while (!interrupted)
{
System.Diagnostics.Debug.WriteLine("Waiting for the message...");
AbstractMessage msg = (AbstractMessage)deserializer.Deserialize(stream);
System.Diagnostics.Debug.WriteLine("Message arrived: " + msg.GetType());
//
// Exit while-loop when receiving a "Connection ends" message.
// Adapt this if condition to whatever is appropriate for
// your AbstractMessage type.
//
if (msg == ConnectionEndsMessage) break;
raiseEvent(msg);
}
}
catch (IOException ex)
{
... handle timeout and other IOExceptions here...
}
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