The zmq_init() function initialises a 0MQ context.
The io_threads argument specifies the size of the 0MQ thread pool to handle I/O operations. If your application is using only the inproc transport for messaging you may set this to zero, otherwise set it to at least one.
Thread safety. A 0MQ
is thread safe and may be shared among as many application threads as necessary, without any additional locking required on the part of the caller.
This function is deprecated by zmq_ctx_new(3).