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Socket.BeginReceive issue with thread blocking
Hi All,
I am having trouble understanding the correct functionality of BeginReceive in the .NET socket object. According to MSDN, BeginReceive will return immediately and the callback function will be run on a separate thread when data is received.
However, I have found that blocking the main thread also causes the receive process to be blocked. From the code below, I would expect to see the following output:
"Listening"
"Data received"
"Return"
This would indicate that the data is correctly received while the main thread sleeps (in real life, it would be doing other work). However, no data is received while the thread sleeps, instead all calls to OnDataReceived only occur after the sleep has ended.
Could anyone shed any light on this?
Many thanks,
Samuele Armondi
I am having trouble understanding the correct functionality of BeginReceive in the .NET socket object. According to MSDN, BeginReceive will return immediately and the callback function will be run on a separate thread when data is received.
However, I have found that blocking the main thread also causes the receive process to be blocked. From the code below, I would expect to see the following output:
"Listening"
"Data received"
"Return"
This would indicate that the data is correctly received while the main thread sleeps (in real life, it would be doing other work). However, no data is received while the thread sleeps, instead all calls to OnDataReceived only occur after the sleep has ended.
Could anyone shed any light on this?
Many thanks,
Samuele Armondi
public class Client
{
private Socket socket;
private AutoResetEvent autoResetEvent;
private IPEndPoint serverEndPoint;
private byte[] buffer;
public bool Connect()
{
//connection code
socket.Connect(serverEndPoint);
//start listening for data
Debug.Print("Listening");
socket.BeginReceive(buffer, 0, buffer.Length, SocketFlags.None, new AsyncCallback(OnDataReceived), null);
Thread.Sleep(1000);
Debug.Print("Return");
}
//Async method called when data is received.
private void OnDataReceived(IAsyncResult res)
{
//handle data
Debug.Print("Data received.");
//carry on receiving
socket.BeginReceive(buffer, 0, buffer.Length, SocketFlags.None, new AsyncCallback(OnDataReceived), null);
}
}
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How are you creating the socket? Â If you are using the SocketInformation class there is an option in SocketInformationOptions to create a NonBlocking socket.
I made some simple modifictaions to your sample and it worked for me.
 1)  Increased the delay (one second might not be long enough):
    Debug.Print("Sleeping");
    do {
      Thread.Sleep(1000);  //Keep sleeping until async result is processed
    } while (!Done);
    Debug.Print("Return");
  2) did not receive again if aync result was complete also set the Done flag:
  private void OnDataReceived(IAsyncResul
  {
    //handle data
    Debug.Print("Data received:"+Encoding.UTF8.G
    if (res.IsCompleted == false)
    {
      //carry on receiving
      socket.BeginReceive(buffer
    }
    Debug.Print("All Done");
    Done = true;
  }
I made some simple modifictaions to your sample and it worked for me.
 1)  Increased the delay (one second might not be long enough):
    Debug.Print("Sleeping");
    do {
      Thread.Sleep(1000);  //Keep sleeping until async result is processed
    } while (!Done);
    Debug.Print("Return");
  2) did not receive again if aync result was complete also set the Done flag:
  private void OnDataReceived(IAsyncResul
  {
    //handle data
    Debug.Print("Data received:"+Encoding.UTF8.G
    if (res.IsCompleted == false)
    {
      //carry on receiving
      socket.BeginReceive(buffer
    }
    Debug.Print("All Done");
    Done = true;
  }
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.NET Programming
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The .NET Framework is not specific to any one programming language; rather, it includes a library of functions that allows developers to rapidly build applications. Several supported languages include C#, VB.NET, C++ or ASP.NET.