ZeroMQ vs Crossroads I/O

Crossroads.io is pretty dead since Martin Sustrik has started on a new stack, in C, called nano: https://github.com/250bpm/nanomsg

Crossroads.io does not, afaik, implement ZMTP/1.0 nor ZMTP/2.0 but its own version of the protocol.

Nano has pluggable transports and we'll probably make a ZMTP transport for that. Nano is really nice, a rethinking of the original libzmq library, and if it's successful would make a good new kernel.

Ideally, Nano would interoperate both at the API and the protocol level, so be a pluggable replacement for libzmq. It does have quite a long way to go, though.

Note that there are now several rewrites of libzmq emerging, including JeroMQ (Java) and NetMQ (C#). These two do implement ZMTP/1.0 and ZMTP/2.0 properly. There are also other libraries like Axon (https://github.com/visionmedia/axon) which are heavily inspired by 0MQ but not compatible.

Based on experience, users value interoperability more than almost anything else, so it's quite likely that different 0MQ-like stacks will end up speaking the same protocols.