Re: TcpClient close() method socket leak
- From: Arthur M. <ArthurM@xxxxxxxxxxxxxxxxxxxxxxxxx>
- Date: Wed, 11 May 2005 06:20:05 -0700
TIME_WAIT is normal behaviour for proper TCP session closure.
Reference blurb from RFC 793 with explanation as to why.
The dirty way to close it is to use RST TCP packet header flag and kill the
connection instead of shutting it down. This is not something you would
consider to be "proper way"
The reason as to why TCP_WAIT is hanging around for 60 seconds - berkley
implementation of a socket states Maximum Segment Lifetime to be 30 seconds,
hence 2 times that is 60 (read below)
The protocol places no restriction on a particular connection being
used over and over again. A connection is defined by a pair of
sockets. New instances of a connection will be referred to as
incarnations of the connection. The problem that arises from this is
-- "how does the TCP identify duplicate segments from previous
incarnations of the connection?" This problem becomes apparent if the
connection is being opened and closed in quick succession, or if the
connection breaks with loss of memory and is then reestablished.
To avoid confusion we must prevent segments from one incarnation of a
connection from being used while the same sequence numbers may still
be present in the network from an earlier incarnation. We want to
assure this, even if a TCP crashes and loses all knowledge of the
sequence numbers it has been using. When new connections are created,
an initial sequence number (ISN) generator is employed which selects a
new 32 bit ISN. The generator is bound to a (possibly fictitious) 32
bit clock whose low order bit is incremented roughly every 4
microseconds. Thus, the ISN cycles approximately every 4.55 hours.
Since we assume that segments will stay in the network no more than
the Maximum Segment Lifetime (MSL) and that the MSL is less than 4.55
hours we can reasonably assume that ISN's will be unique.
"Daniel" wrote:
> also, even after the client executable is unloaded from memory the ever evil
> socket entries remain for 60 seconds:
> [System Process]:0 TCP foobox:8888 localhost:2188 TIME_WAIT
> [System Process]:0 TCP foobox:8888 localhost:2189 TIME_WAIT
> [System Process]:0 TCP foobox:8888 localhost:2190 TIME_WAIT
>
> is it that i can only do 3000 open, send, close in every 60 seconds per a
> limitation w/ the TcpClient or is there something else i could try?
>
> "Daniel" <softwareengineer98037@xxxxxxxxx> wrote in message
> news:%232BHexHEFHA.2540@xxxxxxxxxxxxxxxxxxxxxxx
> > TcpClient close() method socket leak
> >
> > when i use TcpClient to open a connection, send data and close the
> TcpClient
> > with myTcpClientInstance.Close(); it takes 60 seconds for the actual
> socket
> > on the client machine to close per my network app the computer fills up w/
> > thousands of these
> >
> > [System Process]:0 TCP foobox:8888 localhost:2188 TIME_WAIT
> > [System Process]:0 TCP foobox:8888 localhost:2189 TIME_WAIT
> > [System Process]:0 TCP foobox:8888 localhost:2190 TIME_WAIT
> > [System Process]:0 TCP foobox:8888 localhost:2191 TIME_WAIT
> > [System Process]:0 TCP foobox:8888 localhost:2192 TIME_WAIT
> > [System Process]:0 TCP foobox:8888 localhost:2193 TIME_WAIT
> >
> > until the "Only one usage of each socket address" error occures. How to
> > work around this? I need to open connect, send data, and close it. i can
> not
> > share connections in my case i have to open, send and close and have the
> > close truely close. and i have to do more then 3k of these in 60 seconds.
> I
> > know this is possible because I have a c version of the client that uses c
> > sockets and it works fine and does not fill with thousands of:
> >
> > [System Process]:0 TCP foobox:8888 localhost:2188 TIME_WAIT
> >
> > Is this a limitation of TcpClient ? or is there a way to truely close a
> > TcpClient imediatly? i tried setting linger option false, no delay true,
> > timeout 0 etc. still no progress the client sockets all get used up w/
> > thousands of
> >
> > [System Process]:0 TCP foobox:8888 localhost:2188 TIME_WAIT
> > [System Process]:0 TCP foobox:8888 localhost:2189 TIME_WAIT
> > [System Process]:0 TCP foobox:8888 localhost:2190 TIME_WAIT
> >
> > until the "Only one usage of each socket address" error occures.
> >
> > here is what my client code looks like:
> >
> > TcpClient myclient;
> > myclient = new TcpClient();
> > LingerOption lingerOption = new LingerOption (false, 0);
> > myclient.LingerState = lingerOption;
> > myclient.NoDelay = true;
> > myclient.ReceiveTimeout = 0;
> > myclient.Connect("foobox", 8888);
> > NetworkStream networkStream ;
> > networkStream = myclient.GetStream();
> > StreamWriter streamWriter ;
> > streamWriter = new StreamWriter(networkStream);
> > string strData = "";
> > strData += "helloworld\0";
> > streamWriter.WriteLine(strData);
> > streamWriter.Flush();
> > streamWriter.Close() ;
> > networkStream.Close();
> > myclient.Close();
> >
> > something missing? should i do more then close? i tried shutdown too.. no
> > progress
> >
> > here is the dummy server code if it matters:
> >
> > public static void Main()
> > {
> > TcpListener tcpListener = new TcpListener(8082);
> > tcpListener.Start();
> > Console.WriteLine("Server Started") ;
> > while(true)
> > {
> > Socket socketForClient = tcpListener.AcceptSocket();
> > try
> > {
> > if(socketForClient.Connected)
> > {
> > Console.WriteLine("Client connected");
> > NetworkStream networkStream = new NetworkStream(socketForClient);
> > StreamReader streamReader = new StreamReader(networkStream);
> > string line = streamReader.ReadLine();
> > streamReader.Close();
> > Console.WriteLine("Read:" +line);
> > }
> > socketForClient.Shutdown(System.Net.Sockets.SocketShutdown.Both);
> > socketForClient.Close();
> > Console.WriteLine("Client disconnected");
> > GC.Collect();
> > Console.WriteLine("Garbage Collected");
> > }
> > catch(Exception e)
> > {
> > Console.WriteLine(e.ToString()) ;
> > }
> > }
> > }
> >
> >
>
>
>
.
- Prev by Date: dotnet blog
- Next by Date: Re: MessageBox.Show VB.Net VIsual Studio 2003
- Previous by thread: dotnet blog
- Next by thread: IDispose grrrrrr
- Index(es):
Relevant Pages
|
