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 Python generated by Kaitai Struct depends on the Python runtime library. You have to install it before you can parse data.
The Python runtime library can be installed from PyPI:
python3 -m pip install kaitaistructParse a local file and get structure in memory:
data = Websocket.from_file("path/to/local/file.bin")
Or parse structure from a bytes:
from kaitaistruct import KaitaiStream, BytesIO
raw = b"\x00\x01\x02..."
data = Websocket(KaitaiStream(BytesIO(raw)))
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
import kaitaistruct
from kaitaistruct import KaitaiStruct, KaitaiStream, BytesIO
from enum import Enum
if getattr(kaitaistruct, 'API_VERSION', (0, 9)) < (0, 9):
raise Exception("Incompatible Kaitai Struct Python API: 0.9 or later is required, but you have %s" % (kaitaistruct.__version__))
class Websocket(KaitaiStruct):
"""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 Opcode(Enum):
continuation = 0
text = 1
binary = 2
reserved_3 = 3
reserved_4 = 4
reserved_5 = 5
reserved_6 = 6
reserved_7 = 7
close = 8
ping = 9
pong = 10
reserved_control_b = 11
reserved_control_c = 12
reserved_control_d = 13
reserved_control_e = 14
reserved_control_f = 15
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.initial_frame = Websocket.InitialFrame(self._io, self, self._root)
if self.initial_frame.header.finished != True:
self.trailing_frames = []
i = 0
while True:
_ = Websocket.Dataframe(self._io, self, self._root)
self.trailing_frames.append(_)
if _.header.finished:
break
i += 1
class FrameHeader(KaitaiStruct):
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.finished = self._io.read_bits_int_be(1) != 0
self.reserved = self._io.read_bits_int_be(3)
self.opcode = KaitaiStream.resolve_enum(Websocket.Opcode, self._io.read_bits_int_be(4))
self.is_masked = self._io.read_bits_int_be(1) != 0
self.len_payload_primary = self._io.read_bits_int_be(7)
self._io.align_to_byte()
if self.len_payload_primary == 126:
self.len_payload_extended_1 = self._io.read_u2be()
if self.len_payload_primary == 127:
self.len_payload_extended_2 = self._io.read_u4be()
if self.is_masked:
self.mask_key = self._io.read_u4be()
@property
def len_payload(self):
if hasattr(self, '_m_len_payload'):
return self._m_len_payload
self._m_len_payload = (self.len_payload_primary if self.len_payload_primary <= 125 else (self.len_payload_extended_1 if self.len_payload_primary == 126 else self.len_payload_extended_2))
return getattr(self, '_m_len_payload', None)
class InitialFrame(KaitaiStruct):
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.header = Websocket.FrameHeader(self._io, self, self._root)
if self.header.opcode != Websocket.Opcode.text:
self.payload_bytes = self._io.read_bytes(self.header.len_payload)
if self.header.opcode == Websocket.Opcode.text:
self.payload_text = (self._io.read_bytes(self.header.len_payload)).decode(u"UTF-8")
class Dataframe(KaitaiStruct):
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.header = Websocket.FrameHeader(self._io, self, self._root)
if self._root.initial_frame.header.opcode != Websocket.Opcode.text:
self.payload_bytes = self._io.read_bytes(self.header.len_payload)
if self._root.initial_frame.header.opcode == Websocket.Opcode.text:
self.payload_text = (self._io.read_bytes(self.header.len_payload)).decode(u"UTF-8")