Example SMTP Server for PV249

Gemfile

source :rubygems

gem "eventmachine"

smtpserver.rb

#!/usr/bin/env ruby

# Example SMTP Server in Ruby for course FI:PV249
#
# @author Jiri Zapletal <[email protected]>
# @license BSD

require 'bundler/setup'
Bundler.require(:default)

module SmtpProtocol
    include EventMachine::Protocols::LineText2

    def post_init
        reset_state
        send_line("220 mail.example.net SMTP Ruby Server")
    end

    def reset_state
        @mail = nil
        @rcpt = []
        @data = ""
    end

    def send_line(data)
        puts "[S] " + data
        send_data(data + "\r\n")
    end

    def receive_line(line)
        puts "[C] " + line

        case
          when m = /^HELO (.*)$/i.match(line)
            send_line "250 Hello"
          when m = /^EHLO (.*)$/i.match(line)
            send_line "250-mail.example.net"
            send_line "250-STARTTLS"
            send_line "250 DSN"
          when m = /^STARTTLS$/i.match(line)
            send_line "220 2.0.0 Ready to start TLS"
            start_tls
          when m = /^MAIL FROM:(.*)$/i.match(line)
            if @from != nil then
                send_line "503 5.5.1 Error: nested MAIL command"
                return
            end
            @from = m[1]
            send_line "250 2.1.0 Ok"
          when m = /^RCPT TO:(.*)/i.match(line)
            if @from == nil then
                send_line "503 5.5.1 Error: need MAIL command"
                return
            end
            @rcpt << m[1]
            send_line "250 2.1.5 Ok"
          when m = /^RSET$/i.match(line)
            reset_state
            send_line "250 2.0.0 Ok"
          when m = /^DATA$/i.match(line)
            if @rcpt.count == 0 then
                send_line "503 5.5.1 Error: need RCPT command"
                return
            end

            send_line "354 End data with <CR><LF>.<CR><LF>"
            set_text_mode
          when m = /^QUIT$/i.match(line)
            send_line "221 Bye"
            close_connection_after_writing
          else
            puts "[error]", line
            send_line "502 5.5.2 Error: command not recognized"
          end
    end

    def receive_binary_data(data)
        print "data", data.inspect
        if /\r\n\.\r\n$/.match(data) then
            @data += data[0..-5]
            id = receive_mail(@from, @rcpt, @data)
            send_line "250 2.0.0 Ok: queued as #{id}"
            reset_state
            set_line_mode
        else
            @data += data
        end
    end

    def unbind
        puts "[C Disconnected]"
    end

    def receive_mail(from, to, data)
        puts "Email from #{from} to #{to.join(",")}"

        return "123456"
    end
end

EventMachine.run do
    Signal.trap("INT")  { EventMachine.stop }
    Signal.trap("TERM") { EventMachine.stop }

    EventMachine.start_server("0.0.0.0", 8025, SmtpProtocol)
end