NetMQ 订阅者使用已发布的消息进行阻塞

Question

我有一个消息发布服务器class，它在构造时使用以下代码创建一个 PUB 套接字：

this.context = NetMQContext.Create();
this.pubSocket = this.context.CreatePublisherSocket();
var portNumber = this.installerSettings.PublisherPort;
this.pubSocket.Bind("tcp://127.0.0.1:" + portNumber);

使用 messagePublishingServer.Publish(message) 发送消息执行：

this.pubSocket.SendMoreFrame(string.Empty).SendFrame(message);

以下 xBehave 测试...

    [Scenario]
    public void PublishMessageScenario()
    {
        MessagePublishingServer messagePublishingServer = null;
        NetMQContext context;
        NetMQ.Sockets.SubscriberSocket subSocket = null;
        string receivedMessage = null;

        "Given a running message publishing server"._(() =>
        {
            var installerSettingsManager = A.Fake<IInstallerSettingsManager>();
            var settings = new InstallerSettings { PublisherPort = "5348" };
            A.CallTo(() => installerSettingsManager.Settings).Returns(settings);
            messagePublishingServer = new MessagePublishingServer(installerSettingsManager);
        });

        "And a subscriber connected to the publishing server"._(() =>
        {
            context = NetMQContext.Create();
            subSocket = context.CreateSubscriberSocket();
            subSocket.Options.ReceiveHighWatermark = 1000;
            subSocket.Connect("tcp://127.0.0.1:5348");
            subSocket.Subscribe(string.Empty);
        });

        "When publishing a message"._(() =>
        {
            messagePublishingServer.Publish("test message");

            // Receive the topic
            subSocket.ReceiveFrameString();

            // and the message
            receivedMessage = subSocket.ReceiveFrameString();
        });

        "Then the subscriber must have received it"._(() =>
        {
            receivedMessage.Should().NotBeNullOrEmpty();
            receivedMessage.Should().Be("test message");
        });
    }

...第一个 subSocket.ReceiveFrameString() 中的块，我发现这是意外的。订阅者套接字不应该在接收被调用之前对发布的消息进行排队吗？

Answer 1

来源（ReceivingSocketExtensions.cs ):

    /// Receive a single frame from socket, blocking until one arrives, and decode as a string using ...
    public static string ReceiveFrameString([NotNull] this IReceivingSocket socket)

和

    /// If no message is immediately available, return <c>false</c>.
    public static bool TryReceiveFrameString([NotNull] this IReceivingSocket socket, out string frameString)

Answer 2

发布者就像收音机，如果发布者发布时您没有连接和订阅，您就会错过消息。我的建议是在订阅者连接后休眠 100 毫秒（仅用于测试）。

NetMQ 订阅者使用已发布的消息进行阻塞

NetMQ subscriber blocking with a published message

c#

publish-subscribe

netmq