module BBS::Telnet

The telnet line I/O of a BBS::Session: option negotiation, key and line input with telnet commands filtered out (Telnet::Parser), ANSI escape and mouse report decoding (Telnet::Keys, Telnet::Mouse), line editing (Telnet::LineInput), window size (NAWS) tracking, and the PETSCII mode for Commodore 64 callers. The including class keeps the socket in +@client+.

Constants

DEFAULT_COLS: The terminal width assumed while the caller has not reported one.
DEFAULT_ROWS: The terminal height assumed while the caller has not reported one.
MAX_COLS: The widest terminal accepted from a NAWS report, in columns.
MAX_ROWS: The tallest terminal accepted from a NAWS report, in rows.
MAX_SUBNEGOTIATION: The most bytes of a subnegotiation kept; the rest is read and dropped.
MIN_COLS: The narrowest terminal accepted from a NAWS report, in columns.
MIN_ROWS: The shortest terminal accepted from a NAWS report, in rows.
NAWS_SIZE: The bytes of a NAWS report: width and height, two bytes each.
NEGOTIATION: The opening negotiation: the server will echo and suppress go-ahead, and asks the client to suppress go-ahead and report its window size.

Public Instance Methods

line ()

Source

# File lib/bbs/telnet.rb, line 101
def line = @client

Returns the caller’s socket itself, for a door that hands it on as it is (BBS::Gateway).

naws_reported? ()

Source

# File lib/bbs/telnet.rb, line 63
def naws_reported? = @naws_reported == true

Returns true once the client has reported its window size (telnet NAWS). Real terminals do; port scanners and password-guessing bots usually do not.

negotiate ()

Source

# File lib/bbs/telnet.rb, line 53
def negotiate
  @term_cols = DEFAULT_COLS
  @term_rows = DEFAULT_ROWS
  send_raw Ansi::CRLF
  send_raw NEGOTIATION
end

Sets the terminal size to 80x24 until the client reports its own, and sends the opening NEGOTIATION.

A line end goes first: the UltimateTerm of the C64 Ultimate takes a line whose first byte is a telnet command (IAC) for ASCII with ANSI and translates every byte from ASCII to PETSCII, which turns CLR into nothing and swaps the case of letters both ways; any other first byte leaves it on PETSCII, printing the bytes as they come.

petscii! ()

Source

# File lib/bbs/telnet.rb, line 86
def petscii!
  return if @petscii

  @mouse_enabled = false
  @term_cols     = Petscii::COLS
  @term_rows     = Petscii::ROWS
  send_raw Petscii.bytes("#{Petscii::LOWERCASE}#{Petscii::LOCK_CASE}#{Petscii::CLEAR}")
  @petscii = Petscii::Encoder.new
end

Switches the line to PETSCII for a Commodore 64 (see BBS::Petscii): sets the size to 40x25, sends the codes for the lowercase character set (locked) and a clear screen, and turns mouse reporting off. From then on write encodes its output and readkey / readline decode PETSCII keys. Does nothing when the line is already in PETSCII mode.

petscii? ()

Source

# File lib/bbs/telnet.rb, line 97
def petscii? = !@petscii.nil?

True when the line is in PETSCII mode (see petscii!).

resize! (cols, rows)

Source

# File lib/bbs/telnet.rb, line 107
def resize!(cols, rows)
  unless @petscii
    @term_cols = cols.clamp(MIN_COLS, MAX_COLS) if cols.positive?
    @term_rows = rows.clamp(MIN_ROWS, MAX_ROWS) if rows.positive?
  end
  @naws_reported = true
end

Sets the caller’s window size from a NAWS report: cols is clamped to MIN_COLS..MAX_COLS and rows to MIN_ROWS..MAX_ROWS, a zero value is ignored, and a PETSCII line keeps 40x25. Marks the size as reported (naws_reported?).

settle (timeout: 1.5)

Source

# File lib/bbs/telnet.rb, line 69
def settle(timeout: 1.5)
  deadline = monotonic + timeout
  until naws_reported?
    left = deadline - monotonic
    raw  = read_byte(left) if left.positive?
    break unless raw.is_a?(String)

    telnet_data(raw.ord)
  end
  self if naws_reported?
end

Waits up to timeout seconds for the client’s answers to the negotiation, its window size above all, and drops whatever it types meanwhile: a bot’s “root” sent before any prompt goes nowhere. Returns self when the window size came, nil when it did not.

write (data)

Source

# File lib/bbs/telnet.rb, line 119
def write(data)
  send_raw(@petscii ? @petscii.encode(data) : data)
rescue IOError
  raise
rescue StandardError
  nil
end

Writes data (a String) to the caller, encoded to PETSCII on a PETSCII line. Returns nil when the write fails, except for a caller who stopped reading: when the write times out (IO::TimeoutError) the line is closed and IOError is raised, which ends the session.

write_raw (data)

Source

# File lib/bbs/telnet.rb, line 130
def write_raw(data) = send_raw(data)

Writes the bytes of data to the caller as they are, not encoded to PETSCII even on a PETSCII line: for binary protocols (BBS::Zmodem, BBS::Xmodem) and telnet commands. Fails as write does.