bbsterm.rb

require 'rubygems'
require 'eventmachine'

module Telnet
  # :stopdoc:
  IAC   = 255.chr # "\377" # "\xff" # interpret as command
  DONT  = 254.chr # "\376" # "\xfe" # you are not to use option
  DO    = 253.chr # "\375" # "\xfd" # please, you use option
  WONT  = 252.chr # "\374" # "\xfc" # I won't use option
  WILL  = 251.chr # "\373" # "\xfb" # I will use option
  SB    = 250.chr # "\372" # "\xfa" # interpret as subnegotiation
  GA    = 249.chr # "\371" # "\xf9" # you may reverse the line
  EL    = 248.chr # "\370" # "\xf8" # erase the current line
  EC    = 247.chr # "\367" # "\xf7" # erase the current character
  AYT   = 246.chr # "\366" # "\xf6" # are you there
  AO    = 245.chr # "\365" # "\xf5" # abort output--but let prog finish
  IP    = 244.chr # "\364" # "\xf4" # interrupt process--permanently
  BREAK = 243.chr # "\363" # "\xf3" # break
  DM    = 242.chr # "\362" # "\xf2" # data mark--for connect. cleaning
  NOP   = 241.chr # "\361" # "\xf1" # nop
  SE    = 240.chr # "\360" # "\xf0" # end sub negotiation
  EOR   = 239.chr # "\357" # "\xef" # end of record (transparent mode)
  ABORT = 238.chr # "\356" # "\xee" # Abort process
  SUSP  = 237.chr # "\355" # "\xed" # Suspend process
  EOF   = 236.chr # "\354" # "\xec" # End of file
  SYNCH = 242.chr # "\362" # "\xf2" # for telfunc calls

  OPT_BINARY         =   0.chr # "\000" # "\x00" # Binary Transmission
  OPT_ECHO           =   1.chr # "\001" # "\x01" # Echo
  OPT_RCP            =   2.chr # "\002" # "\x02" # Reconnection
  OPT_SGA            =   3.chr # "\003" # "\x03" # Suppress Go Ahead
  OPT_NAMS           =   4.chr # "\004" # "\x04" # Approx Message Size Negotiation
  OPT_STATUS         =   5.chr # "\005" # "\x05" # Status
  OPT_TM             =   6.chr # "\006" # "\x06" # Timing Mark
  OPT_RCTE           =   7.chr # "\a"   # "\x07" # Remote Controlled Trans and Echo
  OPT_NAOL           =   8.chr # "\010" # "\x08" # Output Line Width
  OPT_NAOP           =   9.chr # "\t"   # "\x09" # Output Page Size
  OPT_NAOCRD         =  10.chr # "\n"   # "\x0a" # Output Carriage-Return Disposition
  OPT_NAOHTS         =  11.chr # "\v"   # "\x0b" # Output Horizontal Tab Stops
  OPT_NAOHTD         =  12.chr # "\f"   # "\x0c" # Output Horizontal Tab Disposition
  OPT_NAOFFD         =  13.chr # "\r"   # "\x0d" # Output Formfeed Disposition
  OPT_NAOVTS         =  14.chr # "\016" # "\x0e" # Output Vertical Tabstops
  OPT_NAOVTD         =  15.chr # "\017" # "\x0f" # Output Vertical Tab Disposition
  OPT_NAOLFD         =  16.chr # "\020" # "\x10" # Output Linefeed Disposition
  OPT_XASCII         =  17.chr # "\021" # "\x11" # Extended ASCII
  OPT_LOGOUT         =  18.chr # "\022" # "\x12" # Logout
  OPT_BM             =  19.chr # "\023" # "\x13" # Byte Macro
  OPT_DET            =  20.chr # "\024" # "\x14" # Data Entry Terminal
  OPT_SUPDUP         =  21.chr # "\025" # "\x15" # SUPDUP
  OPT_SUPDUPOUTPUT   =  22.chr # "\026" # "\x16" # SUPDUP Output
  OPT_SNDLOC         =  23.chr # "\027" # "\x17" # Send Location
  OPT_TTYPE          =  24.chr # "\030" # "\x18" # Terminal Type
  OPT_EOR            =  25.chr # "\031" # "\x19" # End of Record
  OPT_TUID           =  26.chr # "\032" # "\x1a" # TACACS User Identification
  OPT_OUTMRK         =  27.chr # "\e"   # "\x1b" # Output Marking
  OPT_TTYLOC         =  28.chr # "\034" # "\x1c" # Terminal Location Number
  OPT_3270REGIME     =  29.chr # "\035" # "\x1d" # Telnet 3270 Regime
  OPT_X3PAD          =  30.chr # "\036" # "\x1e" # X.3 PAD
  OPT_NAWS           =  31.chr # "\037" # "\x1f" # Negotiate About Window Size
  OPT_TSPEED         =  32.chr # " "    # "\x20" # Terminal Speed
  OPT_LFLOW          =  33.chr # "!"    # "\x21" # Remote Flow Control
  OPT_LINEMODE       =  34.chr # "\""   # "\x22" # Linemode
  OPT_XDISPLOC       =  35.chr # "#"    # "\x23" # X Display Location
  OPT_OLD_ENVIRON    =  36.chr # "$"    # "\x24" # Environment Option
  OPT_AUTHENTICATION =  37.chr # "%"    # "\x25" # Authentication Option
  OPT_ENCRYPT        =  38.chr # "&"    # "\x26" # Encryption Option
  OPT_NEW_ENVIRON    =  39.chr # "'"    # "\x27" # New Environment Option
  OPT_EXOPL          = 255.chr # "\377" # "\xff" # Extended-Options-List

  NULL = "\000"
  CR   = "\015"
  LF   = "\012"
  EOL  = CR + LF

  def preprocess(string)
    # combine CR+NULL into CR
    string = string.gsub(/#{CR}#{NULL}/no, CR)

    # combine EOL into "\n"
    string = string.gsub(/#{EOL}/no, "\n")

    # remove NULL
    string = string.gsub(/#{NULL}/no, '')

    string.gsub(/#{IAC}(
                  [#{IAC}#{AO}#{AYT}#{DM}#{IP}#{NOP}]|
                  [#{DO}#{DONT}#{WILL}#{WONT}]
                    [#{OPT_BINARY}-#{OPT_NEW_ENVIRON}#{OPT_EXOPL}]|
                  #{SB}[^#{IAC}]*#{IAC}#{SE}
                )/xno) do
                          if    IAC == $1  # handle escaped IAC characters
                            IAC
                          elsif AYT == $1  # respond to "IAC AYT" (are you there)
                            send_data("nobody here but us pigeons" + EOL)
                              ''
                          elsif DO[0] == $1[0]  # respond to "IAC DO x"
                            if OPT_BINARY[0] == $1[1]
                              @telnet_option["BINARY"] = true
                              send_data(IAC + WILL + OPT_BINARY)
                            else
                              send_data(IAC + WONT + $1[1..1])
                            end
                              ''
                          elsif DONT[0] == $1[0]  # respond to "IAC DON'T x" with "IAC WON'T x"
                            send_data(IAC + WONT + $1[1..1])
                              ''
                          elsif WILL[0] == $1[0]  # respond to "IAC WILL x"
                            if    OPT_BINARY[0] == $1[1]
                              send_data(IAC + DO + OPT_BINARY)
                            elsif OPT_ECHO[0] == $1[1]
                              send_data(IAC + DO + OPT_ECHO)
                            elsif OPT_SGA[0]  == $1[1]
                              @sga = true
                              send_data(IAC + DO + OPT_SGA)
                            else
                              send_data(IAC + DONT + $1[1..1])
                            end
                              ''
                          elsif WONT[0] == $1[0]  # respond to "IAC WON'T x"
                            if    OPT_ECHO[0] == $1[1]
                              send_data(IAC + DONT + OPT_ECHO)
                            elsif OPT_SGA[0]  == $1[1]
                              @sga = false
                              send_data(IAC + DONT + OPT_SGA)
                            else
                              send_data(IAC + DONT + $1[1..1])
                            end
                              ''
                          else
                              ''
                          end
                end
  end
end

module DOSCODE
  def dos2utf8(s)
    s.encode(Encoding::UTF_8, Encoding::IBM437, :crlf_newline => true)
  end

  def utf82dos(s)
    s.encode(Encoding::IBM437, Encoding::UTF_8, :crlf_newline => true)
  end
end

class BBSTerm < EM::Connection
  include DOSCODE
  include Telnet

  def post_init
    @initialization = true
    @read_buffer = ""
  end

  def receive_data(data)
    result = @read_buffer + data
    @read_buffer.clear

    if Integer(data.rindex(/#{IAC}#{SE}/no) || 0) <
        Integer(data.rindex(/#{IAC}#{SB}/no) || 0)
      result = preprocess(data[0 ... data.rindex(/#{IAC}#{SB}/no)])
      @read_buffer += data[data.rindex(/#{IAC}#{SB}/no) .. -1]
    elsif pt = data.rindex(/#{IAC}[^#{IAC}#{AO}#{AYT}#{DM}#{IP}#{NOP}]?\z/no) ||
        data.rindex(/\r\z/no)
      result = preprocess(data[0 ... pt])
      @read_buffer += data[pt .. -1]
    else
      result = preprocess(data)
      rest = ''
    end
    result = dos2utf8(result)

    if @initialization and result =~ /\e\[6n/
      @initialization = false
      send_data "\e[1a\r\n"
    end

    $stdout.print result
    $stdout.flush
  end
end

class STDINReader < EM::Connection
  include DOSCODE

  def initialize(em)
    @em = em
  end

  def post_init
    @em.send_data "\xff\xf2"
    @em.send_data "\xff\xfb\x18"
    @em.send_data "\xff\xfa\x18\x00ANSI\xff\xf0"
  end

  def receive_data(data)
    if data =~ /\cC/
      restore_tty
      exit
    end
    
    data = utf82dos(data)

    data.gsub!(/\x7f/) { "\b" }
    EM.next_tick { @em.send_data(data) }
  end
end

$tty = `tty`.chomp
$stty = `stty -g`.chomp
system("stty raw")

def restore_tty
  system("stty -f #{$tty} '#{$stty}'")
end

Signal.trap("INT") do 
  restore_tty
end

at_exit do
  restore_tty
end

EM.run do 
  obj = EM.connect(ARGV[0], ARGV[1] || 2002, BBSTerm)
  EM.open_keyboard(STDINReader, obj)
end