The WebSocket protocol establishes a two-way communication channel via TCP.
Messages are made up of one or more dataframes, and are delineated by
frames with the fin
bit set.
This page hosts a formal specification of WebSocket using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.
All parsing code for Ruby generated by Kaitai Struct depends on the Ruby runtime library. You have to install it before you can parse data.
The Ruby runtime library can be installed from RubyGems:
gem install kaitai-struct
Parse a local file and get structure in memory:
data = Websocket.from_file("path/to/local/file.bin")
Or parse structure from a string of bytes:
bytes = "\x00\x01\x02..."
data = Websocket.new(Kaitai::Struct::Stream.new(bytes))
After that, one can get various attributes from the structure by invoking getter methods like:
data.initial_frame # => get initial frame
# This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild
require 'kaitai/struct/struct'
unless Gem::Version.new(Kaitai::Struct::VERSION) >= Gem::Version.new('0.9')
raise "Incompatible Kaitai Struct Ruby API: 0.9 or later is required, but you have #{Kaitai::Struct::VERSION}"
end
##
# The WebSocket protocol establishes a two-way communication channel via TCP.
# Messages are made up of one or more dataframes, and are delineated by
# frames with the `fin` bit set.
class Websocket < Kaitai::Struct::Struct
OPCODE = {
0 => :opcode_continuation,
1 => :opcode_text,
2 => :opcode_binary,
3 => :opcode_reserved_3,
4 => :opcode_reserved_4,
5 => :opcode_reserved_5,
6 => :opcode_reserved_6,
7 => :opcode_reserved_7,
8 => :opcode_close,
9 => :opcode_ping,
10 => :opcode_pong,
11 => :opcode_reserved_control_b,
12 => :opcode_reserved_control_c,
13 => :opcode_reserved_control_d,
14 => :opcode_reserved_control_e,
15 => :opcode_reserved_control_f,
}
I__OPCODE = OPCODE.invert
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@initial_frame = InitialFrame.new(@_io, self, @_root)
if initial_frame.header.finished != true
@trailing_frames = []
i = 0
begin
_ = Dataframe.new(@_io, self, @_root)
@trailing_frames << _
i += 1
end until _.header.finished
end
self
end
class FrameHeader < Kaitai::Struct::Struct
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@finished = @_io.read_bits_int_be(1) != 0
@reserved = @_io.read_bits_int_be(3)
@opcode = Kaitai::Struct::Stream::resolve_enum(Websocket::OPCODE, @_io.read_bits_int_be(4))
@is_masked = @_io.read_bits_int_be(1) != 0
@len_payload_primary = @_io.read_bits_int_be(7)
@_io.align_to_byte
if len_payload_primary == 126
@len_payload_extended_1 = @_io.read_u2be
end
if len_payload_primary == 127
@len_payload_extended_2 = @_io.read_u4be
end
if is_masked
@mask_key = @_io.read_u4be
end
self
end
def len_payload
return @len_payload unless @len_payload.nil?
@len_payload = (len_payload_primary <= 125 ? len_payload_primary : (len_payload_primary == 126 ? len_payload_extended_1 : len_payload_extended_2))
@len_payload
end
attr_reader :finished
attr_reader :reserved
attr_reader :opcode
attr_reader :is_masked
attr_reader :len_payload_primary
attr_reader :len_payload_extended_1
attr_reader :len_payload_extended_2
attr_reader :mask_key
end
class InitialFrame < Kaitai::Struct::Struct
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@header = FrameHeader.new(@_io, self, @_root)
if header.opcode != :opcode_text
@payload_bytes = @_io.read_bytes(header.len_payload)
end
if header.opcode == :opcode_text
@payload_text = (@_io.read_bytes(header.len_payload)).force_encoding("UTF-8")
end
self
end
attr_reader :header
attr_reader :payload_bytes
attr_reader :payload_text
end
class Dataframe < Kaitai::Struct::Struct
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@header = FrameHeader.new(@_io, self, @_root)
if _root.initial_frame.header.opcode != :opcode_text
@payload_bytes = @_io.read_bytes(header.len_payload)
end
if _root.initial_frame.header.opcode == :opcode_text
@payload_text = (@_io.read_bytes(header.len_payload)).force_encoding("UTF-8")
end
self
end
attr_reader :header
attr_reader :payload_bytes
attr_reader :payload_text
end
attr_reader :initial_frame
attr_reader :trailing_frames
end