NullPointerException: Cannot invoke "zmq.IMailbox.send(zmq.Command)" because "this.slots[tid]" is null about jeromq

[fbacchella]

Did you try with release 0.6.0 ?

[inad9300]

I confirm this exception can occur in 0.6.0 (this happens sometimes in a scenario like the one described in #984; both issues may be due to the same underlying problem):

Exception in thread "ZMonitor-Sub[56]" java.lang.NullPointerException: Cannot invoke "zmq.IMailbox.send(zmq.Command)" because "this.slots[tid]" is null
        at zmq.Ctx.sendCommand(Ctx.java:662)
        at zmq.ZObject.sendCommand(ZObject.java:410)
        at zmq.ZObject.sendReapAck(ZObject.java:290)
        at zmq.SocketBase.processCommands(SocketBase.java:1183)
        at zmq.SocketBase.send(SocketBase.java:854)
        at zmq.SocketBase.send(SocketBase.java:792)
        at org.zeromq.ZMQ$Socket.send(ZMQ.java:3445)
        at org.zeromq.ZMQ$Socket.send(ZMQ.java:3359)
        at org.zeromq.ZStar$Plateau.run(ZStar.java:503)
        at org.zeromq.ZThread$ShimThread.run(ZThread.java:57)