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c#cancellationthread-abort
Murhaf Sousli
Murhaf Sousli

Reputation: 13306

Thread.Abort() stucks at NetworkStream.Read?

I have a file transfer application (server-client) ... while sending a file, i want to enable cancellation.
Client Cancel the SendFile method that it works by backgroundworker then it sends a command to the server to cancel its receiving thread.
when server receives this command it calls Stop method but it stucks in that line network.Read(data, 0, data.Length);

how can i abort this thread and go to finally without stucking in network.Read(..) ??
thanks in advance.

Thread thTransferFile = null;

void Start()
{
    thTransferFile = new Thread(unused => ft.Receive(destPath, Convert.ToInt64(fileSize);
    thTransferFile.Start();
}

void Stop()
{
    thTransferFile.Abort();
}


public void Receive(string destPath, long fileSize)
    {
        using (fs = new FileStream(destPath, FileMode.Create, FileAccess.Write))
        {
            try
            {
                int count = 0;
                long sum = 0;
                data = new byte[packetSize];
                while (sum < fileSize)
                {
                    count = network.Read(data, 0, data.Length);   //thread stucks in this line when i abort it
                    fs.Write(data, 0, count);
                    sum += count;
                }
            }
            finally
            {
                network.Write(new byte[1], 0, 1); //tell client that the file transfer ends
                network.Flush();
                fs.Dispose();
                if (Thread.CurrentThread.ThreadState == ThreadState.AbortRequested)
                {
                    File.Delete(destPath);
                }
            }
      }

Upvotes: 0

Views: 3199

Answers (3)

Murhaf Sousli
Murhaf Sousli

Reputation: 13306

i've found a solution when i cancel sending from client side .. the network.DataAvailable set to false .. so i added this line to my receive method in the server

in the while loop:

                while (sum < fileSize)
                {
                    if (network.DataAvailable)
                    {
                        count = network.Read(data, 0, data.Length);
                        fs.Write(data, 0, count);
                        sum += count;
                    }
                }

so it will never stuck at network.Read anymore. it totally worked

Upvotes: 0

Tung
Tung

Reputation: 5444

NetworkStream.Read is blocked until it receives data. Set a timeout on the read operation by using NetworkStream's ReadTimeoutRead the community comment. Also, you may want to reconsider using Abort() to kill your thread. Add a boolean flag in your while loop, and set that flag to false when Stop() is called. This stop flag, combined with a ReadTimeout will ensure that your program eventually exits.

The thread that calls Abort might block if the thread that is being aborted is in a protected region of code, such as a catch block, finally block, or constrained execution region. If the thread that calls Abort holds a lock that the aborted thread requires, a deadlock can occur.

Upvotes: 1

Daniel Mošmondor
Daniel Mošmondor

Reputation: 19986

Instead of aborting the thread, Close() the network. It will throw the exception like you are expecting.

Killing threads is a big no-no, since there are resources that can be left uncleaned...

Upvotes: 1

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