经销商交易 - 无序消息

Question

作为ROUTER to DEALER的后续行动，我有一个DEALER与单个ROUTER交谈：

简而言之，我为每个DEALER创建了2个主题。 DEALER的生命周期是：

1. 将READY发送至ROUTER以表明ROUTER可以信任KILL来自它的信号
2. 等待来自ROUTER
的确认
3. 发送5条消息

4. 发送END消息，以便ROUTER退出

   package net.async

   import org.zeromq.ZMQ
   import org.zeromq.ZMQ.Socket
   
   import scala.annotation.tailrec
   
   object Client {
     val Empty           = "".getBytes
     def message(x: Int) = s"HELLO_#$x".getBytes
     val Count   = 5
   }
   
   class Client(name: String) extends Runnable {
   
     import Client._
     import AsyncClientServer._
   
     override def run(): Unit = {
       val context = ZMQ.context(1)
       val dealer = context.socket(ZMQ.DEALER)
       dealer.setIdentity(name.getBytes)
       dealer.connect(s"tcp://localhost:$Port")
       initiate(dealer)
     }
   
     private def initiate(dealer: Socket): Unit = {
       dealer.send("".getBytes, ZMQ.SNDMORE)
       dealer.send("READY".getBytes, 0)
       val reply = new String(dealer.recv(0))
       println(s"DEALER: ${new String(dealer.getIdentity)} received $reply")
       if(reply == Ack) {println("DEALER: received ACK!"); runHelper(dealer, Count)}
       else              initiate(dealer)
     }
   
     @tailrec
     private def runHelper(dealer: Socket, count: Int): Unit = {
       val msg = if(count <= 0 ) End.getBytes else message(count)
       dealer.send(msg, 0)
       val id = new String(dealer.getIdentity)
       println(s"DEALER ${id} sent message: ${new String(msg)}.")
       // println(s"Dealer: ${dealer.getIdentity} received message: " + new String(dealer.recv(0)))
       runHelper(dealer, count - 1)
     }
   }
   
   object AsyncClientServer {
   
     val End = "END"
     val Ack = "WORLD"
     val Port = 5555
     val ClientReady = "READY"
     val Empty = "".getBytes
   
     val context = ZMQ.context(1)
     val router  = context.socket(ZMQ.ROUTER)
   
     def main(args: Array[String]): Unit = {
       router.bind(s"tcp://*:$Port")
       new Thread(new Client("JOE")).start()
       //new Thread(new Client("JILL")).start()
       mainHelper(List.empty)
     }
   
     private def mainHelper(activeClients: List[String]): Unit = {
       val identity = new String( router.recv(0) )
       println(s"ROUTER: Received message from $identity.")
       val empty   = router.recv(0)
       println("ROUTER: received empty: " + new String(empty))
       val message = new String( router.recv(0) )
       println(s"ROUTER: received message: $message")
   
       checkMessage(identity, message, activeClients) match {
         case Normal(msg)     => mainHelper(activeClients)
         case Ready(id)       => ackDealer(router, id); mainHelper(id :: activeClients)
         case Kill            => sys.exit(0)
         case UnknownIdentity => mainHelper(activeClients)
       }
     }
   
     private def ackDealer(router: Socket, identity: String): Unit = {
       router.send(identity.getBytes, ZMQ.SNDMORE)
       router.send(Empty,             ZMQ.SNDMORE)
       router.send(Ack.getBytes,      0)
     }
   
     private def checkMessage(identity: String, message: String, activeClients: List[String]): Message = {
       if(message == ClientReady) Ready(identity)
       else {
         activeClients.find(_ == identity) match {
           case Some(_) =>
             if (message == End) Kill
             else                Normal(message)
           case None    =>       UnknownIdentity
         }
       }
     }
     sealed trait Message
     case class Normal(value: String) extends Message
     case class Ready(id: String)     extends Message
     case object Kill                 extends Message
     case object UnknownIdentity extends Message
   
   }
   

但是，ROUTER似乎无法接收消息：

[info] Running net.async.AsyncClientServer
[info] ROUTER: Received message from JOE.
[info] ROUTER: received empty:
[info] ROUTER: received message: READY
[info] DEALER: JOE received
[info] DEALER: JOE received WORLD
[info] DEALER: received ACK!
[info] ROUTER: Received message from JOE.
[info] ROUTER: received empty:
[info] ROUTER: received message: READY
[info] DEALER JOE sent message: HELLO_#5.
[info] DEALER JOE sent message: HELLO_#4.
[info] DEALER JOE sent message: HELLO_#3.
[info] DEALER JOE sent message: HELLO_#2.
[info] ROUTER: Received message from JOE.
[info] DEALER JOE sent message: HELLO_#1.
[info] ROUTER: received empty: HELLO_#5

最后[info]表示ROUTER收到HELLO_#5的内容应为空。那是为什么？

Answer 1

在initiate中，您正确发送了一个空框架，然后是内容

dealer.send("".getBytes, ZMQ.SNDMORE)
dealer.send("READY".getBytes, 0)

但是在runHelper中，您只发送内容

dealer.send(msg, 0)