How to abort socket's BeginReceive()?

Question

Naturally, BeginReceive() will never end if there\'s no data. MSDN suggests that calling Close() would abort BeginReceive().

Answer 1

In the ReceiveCallback I checked client.Connected within the try block. Now, when data is received after BeginReceive, I can call client.Close(); This way, I do not see exceptions. I send modbus-TCP requests every 200mS, and get responses in time. The console output looks clean. I used a windows forms app, to test this.

    private static void ReceiveCallback(IAsyncResult ar)
    {
        try
        {
            // Retrieve the state object and the client socket
            // from the asynchronous state object.  
            StateObject state = (StateObject)ar.AsyncState;
            Socket client = state.workSocket;
            if (client.Connected)
            {
                // Read data from the remote device.  
                state.dataSize = client.EndReceive(ar);
                if (state.dataSize > 0)
                {
                    Console.WriteLine("Received: " + state.dataSize.ToString() + " bytes from server");
                    // There might be more data, so store the data received so far.  
                    state.sb.Append(Encoding.ASCII.GetString(state.buffer, 0, state.dataSize));
                    //  Get the rest of the data.  
                    client.BeginReceive(state.buffer, 0, StateObject.BUFFER_SIZE, 0,
                        new AsyncCallback(ReceiveCallback), state);

                    state.dataSizeReceived = true;           //received data size?

                    dataSize = state.dataSize;
                    buffer = state.buffer.ToArray();
                    dataSizeReceived = state.dataSizeReceived;

                    string hex = ByteArrayToString(state.buffer, state.dataSize);
                    Console.WriteLine("<- " + hex);

                    receiveDone.Set();
                    client.Close();
                }
                else
                {
                    Console.WriteLine("All the data has arrived");
                    // All the data has arrived; put it in response.  
                    if (state.sb.Length > 1)
                    {
                        Console.WriteLine("Length: " + state.sb.Length.ToString());
                    }
                    // Signal that all bytes have been received.  
                    receiveDone.Set();
                }
            }
        }
        catch (Exception e)
        {
            Console.WriteLine(e.ToString());
        }
    }