CHANNEL socket type (RFC 52).
Single-frame, bidirectional, exclusive pair. Like PAIR but restricted to single-frame messages (draft socket).
require "omq"
require "omq/channel"
ch1 = OMQ::CHANNEL.bind("tcp://127.0.0.1:5555")
ch2 = OMQ::CHANNEL.connect("tcp://127.0.0.1:5555")
ch1 << "ping"
ch2.receive # => "ping"
ch2 << "pong"
ch1.receive # => "pong"