The best replacement for zeromq is rabbitmq.

The best alternatives to zeromq are rated as following:
★★★★★  rabbitmq
★★  gearman
★★  redis
★★  kafka
★★  activemq
★★  nanomsg
★★  amqp
★★  netty
★★  akka
★  redis pubsub
★  msmq
★  dds
★  twisted
  crossroads
  asio

Your alternative for zeromq is not listed? Suggest!
Speaking about zeromq, one probably shouldn't forget about protocol buffers.

Other search terms related to zeromq and their ratings are:
★★★★★ protocol buffers
You have in mind a companion for zeromq and it is not yet here? Propose!



Google Trends

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zeromq
rabbitmq
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