异步套接字阻塞 UI 线程

Question

有关上下文，请参阅我之前的问题：Asynchronous socket calls freezing UI Thread

问题出在客户端，连接到服务器或发送没有问题，但是当调用“OnReceive”方法时，整个客户端停止响应。（它不会 100% 停止它偶尔会响应，但在一个荒谬的响应之后时间为 30 秒+）。其余的调用运行良好，但 UI 不会响应。服务器响应也很好。

StateObject 类：

 class StateObject
    {
        // Client socket.
        public Socket workSocket = null;
        // Size of receive buffer.
        public const int BufferSize = 256;
        // Receive buffer.
        public byte[] buffer = new byte[BufferSize];
        // Received data string.
        public StringBuilder sb = new StringBuilder();
    }

OnConnect 方法：

private void OnConnect(IAsyncResult ar)
        {
            StateObject state = new StateObject();
            try
            {
                Socket client = (Socket)ar.AsyncState;
                client.EndConnect(ar);
               // StateObject state = new StateObject();
                state.workSocket = client;
                //We are connected so we login into the server
                Data msgToSend = new Data();
                msgToSend.cmdCommand = Command.Login;
                msgToSend.strName = textBox2.Text;
                msgToSend.strMessage = null;

                byte[] b = msgToSend.ToByte();

                //Send the message to the server
                //HERE - Starts freezing the UI thread, continues to do background operations
                state.workSocket.BeginSend(b, 0, b.Length, SocketFlags.None, new AsyncCallback(OnSend), state.workSocket);

                //byte[] byteBuffer = new byte[1024];
                state.workSocket.BeginReceive(state.buffer,
                                       0,
                                       state.buffer.Length,
                                       SocketFlags.None,
                                       new AsyncCallback(OnReceive),
                                       state);
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message, "SGSclient", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }

            panel4.Visible = false;
            panel1.Visible = true;
        }

OnReceive 方法：

public void OnReceive(IAsyncResult ar)
        {
            try
            {
                StateObject state = (StateObject)ar.AsyncState;
                Socket client = state.workSocket;
                client.EndReceive(ar);

                Data msgReceived = new Data(state.buffer);
                //Accordingly process the message received
                switch (msgReceived.cmdCommand)
                {
                    case Command.Login:
                        //lstChatters.Items.Add(msgReceived.strName);
                        break;

                    case Command.Logout:
                        //lstChatters.Items.Remove(msgReceived.strName);
                        break;

                    case Command.Message:
                        break;

                    case Command.List:
                        MessageBox.Show(msgReceived.strName);
                        //contacts.Add(msgReceived.strName);
                        needUpdate = true;
                        //lstChatters.Items.AddRange(msgReceived.strMessage.Split('*'));
                        //lstChatters.Items.RemoveAt(lstChatters.Items.Count - 1);
                        //txtChatBox.Text += "<<<" + strName + " has joined the room>>>\r\n";

                        break;
                }

                state.buffer = new byte[256];

               /* client.BeginReceive(byteData,
                                          0,
                                          byteData.Length,
                                          SocketFlags.None,
                                          new AsyncCallback(OnReceive),
                                          client);*/

            }
            catch (ObjectDisposedException)
            { }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message, "SGSclientTCP: " + strName, MessageBoxButtons.OK, MessageBoxIcon.Error);
            }

        }

Answer 1

每当您尝试在 gui 上修改某些内容时，请使用 Invoke 或 BeginInvoke。 我试图更新你的代码，也许我在 vs 中编辑时留下了一些评论。

private void OnConnect(IAsyncResult ar)
    {
        StateObject state = new StateObject();
        try
        {
            Socket client = (Socket)ar.AsyncState;
            client.EndConnect(ar);
            // StateObject state = new StateObject();
            state.workSocket = client;
            //We are connected so we login into the server
            Data msgToSend = new Data();
            msgToSend.cmdCommand = Command.Login;
            msgToSend.strName = textBox2.Text;
            msgToSend.strMessage = null;

            byte[] b = msgToSend.ToByte();

            //Send the message to the server
            //HERE - Starts freezing the UI thread, continues to do background operations
            state.workSocket.BeginSend(b, 0, b.Length, SocketFlags.None, new AsyncCallback(OnSend),
                state.workSocket);

            state.workSocket.BeginReceive(state.buffer,
                0,
                state.buffer.Length,
                SocketFlags.None,
                new AsyncCallback(OnReceive),
                state);
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message, "SGSclient", MessageBoxButtons.OK, MessageBoxIcon.Error);
        }

        //use this when you want to update the gui
        this.BeginInvoke(new MethodInvoker(() =>
        {
            //panel4.Visible = false;
            //panel1.Visible = true;
        }));

    }

    public void OnReceive(IAsyncResult ar)
    {
        String content = String.Empty;
        try
        {
            StateObject state = (StateObject)ar.AsyncState;
            Socket handler = state.workSocket;

            // Read data from the client socket. 
            int bytesRead = handler.EndReceive(ar);

            if (bytesRead > 0)
            {
                // There  might be more data, so store the data received so far.
                state.sb.Append(Encoding.ASCII.GetString(
                    state.buffer, 0, bytesRead));

                // Check for end-of-file tag. If it is not there, read 
                // more data.
                content = state.sb.ToString();
                if (content.IndexOf("<EOF>") > -1)
                {
                    // All the data has been read from the 
                    // client. Display it on the console.
                    //do something with the data, if you update gui use BeginInvoke:

                    //all your bytes are in state.sb


                    Data msgReceived = new Data(state.buffer);
                    //Accordingly process the message received
                    switch (msgReceived.cmdCommand)
                    {
                        case Command.Login:
                            //lstChatters.Items.Add(msgReceived.strName);
                            break;

                        case Command.Logout:
                            //lstChatters.Items.Remove(msgReceived.strName);
                            break;

                        case Command.Message:
                            break;

                        case Command.List:
                            MessageBox.Show(msgReceived.strName);
                            //contacts.Add(msgReceived.strName);
                            needUpdate = true;

//Here you can use BeginInvoke or invoke   
//lstChatters.Items.AddRange(msgReceived.strMessage.Split('*'));
                    //        //lstChatters.Items.RemoveAt(lstChatters.Items.Count - 1);
                    //        //txtChatBox.Text += "<<<" + strName + " has joined the room>>>\r\n";

                    //        break;
                    //}
                }
            } else {
            // Not all data received. Get more.
            handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,
            new AsyncCallback(OnReceive), state);
        }

        }
        catch (ObjectDisposedException)
        { }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message, "SGSclientTCP: " + strName, MessageBoxButtons.OK, MessageBoxIcon.Error);
        }

    }