client.rb

require 'bundler/setup'
require 'eventmachine'

module Handler
  include EM::Deferrable

  def connection_completed
    start_tls(verify_peer: false)
  end

  def ssl_handshake_completed
    succeed
  end
end

EM.epoll
EM.run do
  EM::Iterator.new(1..(ARGV.first.to_i || 999), 5).each do |n, iter|
    EM.connect('127.0.0.1', 1234, Handler) do |c|
      c.callback do
        c.send_data("ping")
        EM.add_timer(0.05) { iter.next }
      end
    end
  end
end

server.rb

require 'bundler/setup'
require 'eventmachine'

module Handler
  def receive_data(data)
    EM.add_timer(10) { close_connection }  if data == "ping"
  end

  def post_init
    start_tls(private_key_file: 'test.key', cert_chain_file: 'test.crt', verify_peer: false)
  end

  def unbind
    puts "closing #{object_id}"
  end
end

puts Process.pid

EM.epoll
EM.run { EM.start_server('127.0.0.1', 1234, Handler) }