NetMQ client to client messaging

Question

I'm trying to create an rpc program to communicate hosts located on different networks and chose Router-Dealer configuration of NetMQ provided here: http://netmq.readthedocs.io/en/latest/router-dealer/#router-dealer

But the problem is that router always selects a random dealer when routing a message to backend. Code which I used :

using (var frontend = new RouterSocket(string.Format("@tcp://{0}:{1}", "127.0.0.1", "5556")))//"@tcp://10.0.2.218:5559"
                using (var backend = new DealerSocket(string.Format("@tcp://{0}:{1}", "127.0.0.1", "5557")))//"@tcp://10.0.2.218:5560"
                {
                    // Handler for messages coming in to the frontend
                    frontend.ReceiveReady += (s, e) =>
                    {
                        Console.WriteLine("message arrived on frontEnd");                            
                        NetMQMessage msg = e.Socket.ReceiveMultipartMessage();
                        string clientAddress = msg[0].ConvertToString();                            
                        Console.WriteLine("Sending to :" + clientAddress);
                        //TODO: Make routing here
                        backend.SendMultipartMessage(msg); // Relay this message to the backend                        };

                    // Handler for messages coming in to the backend
                    backend.ReceiveReady += (s, e) =>
                    {
                        Console.WriteLine("message arrived on backend");
                        var msg = e.Socket.ReceiveMultipartMessage();

                        frontend.SendMultipartMessage(msg); // Relay this message to the frontend
                    };

                    using (var poller = new NetMQPoller { backend, frontend })
                    {
                        // Listen out for events on both sockets and raise events when messages come in
                        poller.Run();
                    }
                }

Code for Client:

using (var client = new RequestSocket(">tcp://" + "127.0.0.1" + ":5556"))
        {
            var messageBytes = UTF8Encoding.UTF8.GetBytes("Hello");
            var messageToServer = new NetMQMessage();
            //messageToServer.AppendEmptyFrame();
            messageToServer.Append("Server2");
            messageToServer.Append(messageBytes);
            WriteToConsoleVoid("======================================");
            WriteToConsoleVoid(" OUTGOING MESSAGE TO SERVER ");
            WriteToConsoleVoid("======================================");
            //PrintFrames("Client Sending", messageToServer);
            client.SendMultipartMessage(messageToServer);

            NetMQMessage serverMessage = client.ReceiveMultipartMessage();
            WriteToConsoleVoid("======================================");
            WriteToConsoleVoid(" INCOMING MESSAGE FROM SERVER");
            WriteToConsoleVoid("======================================");
            //PrintFrames("Server receiving", clientMessage);
            byte[] rpcByteArray = null;
            if (serverMessage.FrameCount == 3)
            {
                var clientAddress = serverMessage[0];
                rpcByteArray = serverMessage[2].ToByteArray();
            }

            WriteToConsoleVoid("======================================");
            Console.ReadLine();
        }

Code for Dealer:

using (var server = new ResponseSocket())
        {
            server.Options.Identity = UTF8Encoding.UTF8.GetBytes(confItem.ResponseServerID);
            Console.WriteLine("Server ID:" + confItem.ResponseServerID);
            server.Connect(string.Format("tcp://{0}:{1}", "127.0.0.1", "5557"));
            using (var poller = new NetMQPoller { server })
            {
                server.ReceiveReady += (s, a) =>
                    {
                        byte[] response = null;
                        NetMQMessage serverMessage = null;
                        try
                        {
                            serverMessage = a.Socket.ReceiveMultipartMessage();
                        }
                        catch (Exception ex)
                        {
                            Console.WriteLine("Exception on ReceiveMultipartMessage : " + ex.ToString());
                            //continue;
                        }
                        byte[] eaBody = null;
                        string clientAddress = "";
                        if (serverMessage.FrameCount == 2)
                        {
                            clientAddress = serverMessage[0].ConvertToString();
                            Console.WriteLine("ClientAddress:" + clientAddress);
                            eaBody = serverMessage[1].ToByteArray();
                            Console.WriteLine("Received message from remote computer: {0} bytes , CurrentID : {1}", eaBody.Length, confItem.ResponseServerID);
                        }
                        else
                        {
                            Console.WriteLine("Received message from remote computer: CurrentID : {0}", confItem.ResponseServerID);
                        }
                    };
                poller.Run();
            }
        }

Is it possible to choose a specific backend on frontend.ReceiveReady? Thanks!

Answer 1

Your backend should be router as well. You need the worker to register or you need to know all the available workers and their identity. When send on the backend push the worker identity at the beginning of the server.

Take a look at the Majordomo example in the zeromq guide:

http://zguide.zeromq.org/page:all#toc72 http://zguide.zeromq.org/page:all#toc98