In ruby you have lowlevel access to all the same methods that you do in C. But you also have some higher level sugar on top of that - and a program that does the same as the c version, is almost as concise as it is in javascript. You get no free concurrency here though - you still need multiple processes or threads to achieve that.
require 'socket'
a = TCPServer.new('', ARGV.first)
connection = a.accept
loop do
connection.write connection.recv(1024)
end