em-ftp-client is a simple EventMachine based FTP Client supporting operations
on stream data.  The primary interface is EventMachine::FtpClient::Session.  A
standard usage would look like:

    require 'eventmachine'
    require 'em-ftp-client'
    
    EM.run do
      EM::FtpClient::Session.new("0.0.0.0", 
        :username => "test", 
        :password => "1234") do |ftp|
        
        ftp.list do |l1|
          puts l1
          puts
          ftp.cwd("files") do
            ftp.list do |l2|
              puts l2
              puts
              ftp.put("one.txt") do
                ftp.stream {|d| puts "STREAMING: #{d.inspect}" }
                ftp.get("two.txt") do |t1|
                  puts "COMPLETED"
                  puts t1
                  puts
                  EM.stop
                end
              end
            end
          end
        end
      end
    end

This library also includes the class SyncSession, which uses fibers and works
with em-synchrony.