How to receive data with ZeroMQ?

问题

I have a simple application which sends and receives data.

ZSocketExample client = new ZSocketExample("127.0.0.1:5555");
client.send("test");

This is my client class:

public class ZSocketExample:IDisposable
{
    public delegate void ReceiveEventHandler(object sender, SocketEventArgs e);

    public event ReceiveEventHandler ReceiveEvent;
    private ZmqContext zmqContext;
    private ZmqSocket zmqSocket;
    private string host;
    private bool isRunning;
    private bool disposed = false;

    public ZSocketExample(string host)
    {
        try
        {
            zmqContext = ZmqContext.Create();
            zmqSocket = zmqContext.CreateSocket(SocketType.DEALER);
            ZHelpers.SetID(zmqSocket, Encoding.UTF8);
            zmqSocket.Connect(host);
            this.isRunning = true;

            zmqSocket.ReceiveReady += new EventHandler<SocketEventArgs>(zmqSocket_ReceiveReady);
            zmqSocket.SendReady += new EventHandler<SocketEventArgs>(zmqSocket_SendReady);

            Poller poller = new Poller(new List<ZmqSocket> { zmqSocket });

            while (isRunning)
            {
                poller.Poll(TimeSpan.FromSeconds(5));
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine(ex.Message);
        }
    }

    void zmqSocket_ReceiveReady(object sender, SocketEventArgs e)
    {
        Console.WriteLine("Receive Ready");
    }

    void zmqSocket_SendReady(object sender, SocketEventArgs e)
    {
        Console.WriteLine("Send Ready");
    }

    public void send(string msg)
    {
        zmqSocket.Send(msg, Encoding.UTF8);

        if (ReceiveEvent != null)
            ReceiveEvent(this, null);
    }

    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }

    protected virtual void Dispose(bool disposing)
    {
        if (disposed)
            return;

        if (disposing)
        {
            close();
        }

        disposed = true;
    }

    public void close()
    {
        isRunning = false;
        zmqSocket.Linger = TimeSpan.FromSeconds(1);
        zmqSocket.Close();
        zmqContext.Terminate();
    }
}

But somehow it doesnot send or receive. Can someone tell me what do I do wrong? And this example blocks the main application. how can I make it non blocking?

回答1:

ZeroMQ socket is not thread safe, you can't use it from multiple threads without using some kind of synchronization.

In your example you call the close which set a variable and then immediately close the socket, this is wrong, you should close the socket when you are out of the while loop.

Regarding receive/send ready, you rarely need to register for send ready, send ready will let you know when you can send a message, in the dealer socket if you are connected you always will be ready to send (unless the highwater has reached).

Receive Ready will be invoked when there is message ready to be received, if other side send you a message the receive ready will be invoked.

For the last part, blocking, you need a dedicate thread to handle zeromq sockets, you can have one thread that handle multiple sockets using the poller.

来源：https://stackoverflow.com/questions/27283464/how-to-receive-data-with-zeromq

标签

zeromq