sock.rb

require 'socket'

class Server
  def call
    File.unlink('socket1')
    File.unlink('socket2')
    server1 = UNIXServer.new('socket1')

    server2 = UNIXServer.new('socket2')
    v = Queue.new
    socks = {
      server1 => 0,
      server2 => 0,
    }

    # socks = {}
    # socks << {}
    # [0, server1.accept]
    # socks << [0, server2.accept]

    Thread.new(socks) do |socks|
      begin
        asocks = socks.keys
        loop do
          ios, _ = IO.select([asocks], [])
          ios.each do |io|
            _ = io[0].read(1)
            vv = v.pop
            io.send_io(vv)
            vv.close

            socks[io] += 1
          end
        end
      rescue => e
        p e
      end
    end

    sock = TCPServer.new(50051)
    sock.listen(Socket::SOMAXCONN)  # TODO make backlog configurable if necessary
    while s = sock.accept
      v.push(s)
    end
  end
end

fork do
  sleep 1
  sock = UNIXSocket.new('socket1')

  loop do
    sock.write_nonblock('v')
    fd = sock.recv_io(TCPSocket)
    puts "socket1"
    sleep 1

    puts fd.gets
    fd.puts("hi")
    fd.close
  end
end

fork do
  sleep 1
  sock = UNIXSocket.new('socket2')

  loop do
    sock.write_nonblock('v')
    fd = sock.recv_io(TCPSocket)
    puts "socket2"
    puts fd.gets
    fd.puts("hi")
    fd.close
  end
end

Server.new.call