我编写了一个Windows服务,使用一个HttpListener异步处理来自点的请求.
它运行正常,但有时会遇到需要重新启动服务或服务器才能修复的问题.最初我用以下方法声明了侦听器对象:
public HttpListener PointsListener = new HttpListener();
这是我开始收听的方法的代码.我是从OnStart服务方法中调用的:
public string ListenerStart()
{
try
{
if (!PointsListener.IsListening)
{
PointsListener.Prefixes.Add(String.Concat("http://*:", points_port, "/"));
PointsListener.Start();
PointsListener.BeginGetContext(PointProcessRequest, PointsListener);
LogWriter("Http listener activated on port " + points_port);
return "Listener started";
}
else
{
return "Listener is already started!";
}
}
catch (Exception err)
{
LogWriter("Error in LIstenerStart \r\n" + err.ToString());
return ("Error: " + err.Message);
}
}
以下是处理请求的方法:
private void PointProcessRequest(IAsyncResult result)
{
HttpListener listener = (HttpListener)result.AsyncState;
HttpListenerContext context = listener.EndGetContext(result);
HttpListenerRequest request = context.Request;
HttpListenerResponse response = context.Response;
response.KeepAlive = false;
System.IO.Stream output = response.OutputStream;
try
{
//declaring a variable for responce
string responseString = "<html>My Response: request is not allowed by server protocol</html>";
// Commands and actions to set responceString
byte[] buffer = Encoding.UTF8.GetBytes(responseString);
response.ContentLength64 = buffer.Length;
output.Write(buffer, 0, buffer.Length);
}
catch (Exception err)
{
LogWriter("Error in PointProcessRequest: \r\n" + err.ToString());
}
finally
{
try
{
output.Flush();
output.Close();
response.Close();
}
catch (Exception err)
{
LogWriter("Error in PointProcessRequest CLOSING OUTPUT STREAM: \r\n" + err.ToString());
}
finally
{
PointsListener.BeginGetContext(PointProcessRequest, PointsListener);
}
}
}
它在某些时候运行良好,但日志中出现以下错误:
Error in PointProcessRequest:
System.Net.HttpListenerException: The specified network name is no longer available
? System.Net.HttpResponseStream.Write(Byte[] buffer, Int32 offset, Int32 size)
? ARK_Dealer.ark.PointProcessRequest(IAsyncResult result)
[26.01.2011 9:00:54] Error in PointProcessRequest CLOSING OUTPUT STREAM:
System.InvalidOperationException: Cannot close stream until all bytes are written.
? System.Net.HttpResponseStream.Dispose(Boolean disposing)
? System.IO.Stream.Close()
? ARK_Dealer.ark.PointProcessRequest(IAsyncResult result)
我认为当某个点将请求发送到服务器但在接收应答失去连接之前,会出现问题.
如何防止抛出异常？响应对象会被自动妥善处理吗？我该如何解决这个问题？
我正在生产中使用HttpListener,我找到了解决这个问题的最好方法,而没有添加一大堆try/catch块,它们无法传达手头代码的逻辑; 是非常简单地设置,Listener.IgnoreWriteExceptions = true;并且,不再写出例外!
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