C#隊列學習筆記：RabbitMQ實現客戶端相互通訊

    一、引言

    fanout類型的Exchange，路由規則非常簡單：它會把所有發送到該Exchange的消息，路由到所有與它綁定的Queue中。假設有一個聊天室，各個客戶端都訂閱在同一fanout exchange type，那每個客戶端發送出來的消息，所有的客戶端都能收到，因為大家都訂閱了。此時，只需要簡單地限制一下，只有是與我有關的消息，才在聊天界面上顯示。這樣，即可達到相互通訊的效果。

    二、示例

    2.1、環境准備

    本示例使用EasyNetQ來實現，請先在NuGet上安裝。

    2.2、實體類

    新建一個實體類MessageBody：

    public class MessageBody
    {
        public string FromUserId { get; set; }
        public string Message { get; set; }
        public string ToUserId { get; set; }
    }

    2.3、主窗體

    新建一個ChatMain窗體：

    代碼如下：

    public partial class ChatMain : Form
    {
        public ChatMain()
        {
            InitializeComponent();
        }

        /// <summary>
        /// 客戶端 A
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void Button1_Click(object sender, EventArgs e)
        {
            ChatWith chatWith = new ChatWith(currentUserId: "UserA")
            {
                StartPosition = FormStartPosition.CenterScreen
            };
            chatWith.Show();
        }

        /// <summary>
        /// 客戶端 B
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void Button2_Click(object sender, EventArgs e)
        {
            ChatWith chatWith = new ChatWith(currentUserId: "UserB")
            {
                StartPosition = FormStartPosition.CenterScreen
            };
            chatWith.Show();
        }

        /// <summary>
        /// 客戶端 C
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void Button3_Click(object sender, EventArgs e)
        {

            ChatWith chatWith = new ChatWith(currentUserId: "UserC")
            {
                StartPosition = FormStartPosition.CenterScreen
            };
            chatWith.Show();

        }

        /// <summary>
        /// 客戶端 D
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void Button4_Click(object sender, EventArgs e)
        {
            ChatWith chatWith = new ChatWith(currentUserId: "UserD")
            {
                StartPosition = FormStartPosition.CenterScreen
            };
            chatWith.Show();
        }
    }

    2.4、客戶端窗體

    新建一個ChatWith窗體：

    代碼如下：

    public partial class ChatWith : Form
    {
        public delegate void ChatWithDelegate();
        public delegate void ChatWithDelegate<T1>(T1 obj1);
        public delegate void ChatWithDelegate<T1, T2>(T1 obj1, T2 obj2);

        public string CurrentUserId { get; }

        private IBus bus;
        public const string ConnStringMQ = "host=192.168.2.242:5672,192.168.2.165:5672;virtualHost=/;username=hello;password=world";
        public const string FanoutExchange = "fanoutEC";

        /// <summary>
        /// 有參構造函數
        /// </summary>
        /// <param name="currentUserId"></param>
        public ChatWith(string currentUserId)
        {
            InitializeComponent();

            //在多線程程序中，新創建的線程不能訪問UI線程創建的窗口控件。
            //此時若想訪問窗體的控件，可將窗體構造函數中的CheckForIllegalCrossThreadCalls設置為false。
            //這時線程就能安全地訪問窗體控件了。
            CheckForIllegalCrossThreadCalls = false;

            CurrentUserId = currentUserId;
        }

        /// <summary>
        /// ShowMessage重載
        /// </summary>
        /// <param name="msg"></param>
        private void ShowMessage(string msg)
        {
            if (InvokeRequired)//InvokeRequired：當前線程不是創建控件的線程時為true
            {
                BeginInvoke(new ChatWithDelegate<string>(ShowMessage), msg);
            }
            else
            {
                ListViewItem item = new ListViewItem(new string[] { DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss"), msg });
                lvwReceiveMsg.Items.Insert(0, item);
            }
        }

        /// <summary>
        /// ShowMessage重載
        /// </summary>
        /// <param name="toUserId"></param>
        /// <param name="msg"></param>
        private void ShowMessage(string toUserId, string msg)
        {
            if (InvokeRequired)
            {
                BeginInvoke(new ChatWithDelegate<string, string>(ShowMessage), toUserId, msg);
            }
            else
            {
                ListViewItem item = new ListViewItem(new string[] { DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss"), toUserId, msg });
                lvwReceiveMsg.Items.Insert(0, item);
            }
        }

        /// <summary>
        /// 綁定隊列並訂閱
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void ChatWith_Load(object sender, EventArgs e)
        {
            cmbOnLine.SelectedIndex = 0;
            Text = Text + $"[{CurrentUserId}]";

            //這里不能使用using，否則訂閱者立即就釋放了，訂閱不到消息。
            bus = RabbitHutch.CreateBus(ConnStringMQ);
            {
                if (bus.IsConnected)
                {
                    var exchange = bus.Advanced.ExchangeDeclare(name: FanoutExchange, type: ExchangeType.Fanout);
                    var queue = bus.Advanced.QueueDeclare(name: $"{FanoutExchange}_queue_{CurrentUserId}");
                    bus.Advanced.Bind(exchange: exchange, queue: queue, routingKey: "");

                    bus.Advanced.Consume(queue, registration =>
                    {
                        registration.Add<MessageBody>((message, info) =>
                        {
                            if (message.Body.ToUserId == CurrentUserId)
                            {
                                ShowMessage(message.Body.FromUserId, message.Body.Message);
                            }
                        });
                    });
                }
                else
                {
                    ShowMessage("服務器連接失敗。");
                }
            }
        }

        /// <summary>
        /// 發送
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void btnSend_Click(object sender, EventArgs e)
        {
            try
            {
                using (var bus = RabbitHutch.CreateBus(ConnStringMQ))
                {
                    if (bus.IsConnected)
                    {
                        if (cmbOnLine.Text == "*")//群發
                        {
                            foreach (var item in cmbOnLine.Items.Cast<string>().Where(s => s != "*" && s != CurrentUserId))
                            {
                                var exchange = bus.Advanced.ExchangeDeclare(name: FanoutExchange, type: ExchangeType.Fanout);
                                var messageBody = new MessageBody
                                {
                                    FromUserId = CurrentUserId,
                                    Message = txtSendMsg.Text,
                                    ToUserId = item
                                };
                                bus.Advanced.Publish(exchange: exchange,
                                    routingKey: "",
                                    mandatory: false,
                                    message: new Message<MessageBody>(messageBody));
                            }
                        }
                        else//私聊
                        {
                            var exchange = bus.Advanced.ExchangeDeclare(name: FanoutExchange, type: ExchangeType.Fanout);
                            var messageBody = new MessageBody
                            {
                                FromUserId = CurrentUserId,
                                Message = txtSendMsg.Text,
                                ToUserId = cmbOnLine.Text
                            };
                            bus.Advanced.Publish(exchange: exchange,
                                routingKey: "",
                                mandatory: false,
                                message: new Message<MessageBody>(messageBody));
                        }
                    }
                    else
                    {
                        ShowMessage("發送消息失敗。");
                    }
                }
            }
            catch (Exception ex)
            {
                ShowMessage(ex.Message);
            }
        }

        /// <summary>
        /// 關閉
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void btnClose_Click(object sender, EventArgs e)
        {
            Close();
        }

        /// <summary>
        /// 窗體關閉事件
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void ChatWith_FormClosed(object sender, FormClosedEventArgs e)
        {
            bus?.Dispose();
        }
    }

    2.5、運行結果