Telethon/telethon/extensions/tcp_client.py

# Python rough implementation of a C# TCP client
import socket
import time
from datetime import datetime, timedelta
from io import BytesIO, BufferedWriter
from threading import Event, Lock
import errno

from ..errors import ReadCancelledError


class TcpClient:
    def __init__(self, proxy=None):
        self._proxy = proxy
        self._socket = None

        # Support for multi-threading advantages and safety
        self.cancelled = Event()  # Has the read operation been cancelled?
        self.delay = 0.1  # Read delay when there was no data available
        self._lock = Lock()

    def _recreate_socket(self, mode):
        if self._proxy is None:
            self._socket = socket.socket(mode, socket.SOCK_STREAM)
        else:
            import socks
            self._socket = socks.socksocket(mode, socket.SOCK_STREAM)
            if type(self._proxy) is dict:
                self._socket.set_proxy(**self._proxy)
            else:  # tuple, list, etc.
                self._socket.set_proxy(*self._proxy)

    def connect(self, ip, port, timeout):
        """Connects to the specified IP and port number.
           'timeout' must be given in seconds
        """
        if not self.connected:
            if ':' in ip:  # IPv6
                self._recreate_socket(socket.AF_INET6)
                self._socket.settimeout(timeout)
                self._socket.connect((ip, port, 0, 0))
            else:
                self._recreate_socket(socket.AF_INET)
                self._socket.settimeout(timeout)
                self._socket.connect((ip, port))
            self._socket.setblocking(False)

    def _get_connected(self):
        return self._socket is not None

    connected = property(fget=_get_connected)

    def close(self):
        """Closes the connection"""
        try:
            if self.connected:
                self._socket.shutdown(socket.SHUT_RDWR)
                self._socket.close()
        except OSError as e:
            if e.errno != errno.ENOTCONN:
                raise
        finally:
            self._socket = None

    def write(self, data):
        """Writes (sends) the specified bytes to the connected peer"""

        # TODO Check whether the code using this has multiple threads calling
        # .write() on the very same socket. If so, have two locks, one for
        # .write() and another for .read().
        try:
            view = memoryview(data)
            total_sent, total = 0, len(data)
            while total_sent < total:
                try:
                    sent = self._socket.send(view[total_sent:])
                    if sent == 0:
                        self.close()
                        raise ConnectionResetError(
                            'The server has closed the connection.')
                    total_sent += sent

                except BlockingIOError:
                    time.sleep(self.delay)
        except BrokenPipeError:
            self.close()
            raise

    def read(self, size, timeout=timedelta(seconds=5)):
        """Reads (receives) a whole block of 'size bytes
           from the connected peer.

           A timeout can be specified, which will cancel the operation if
           no data has been read in the specified time. If data was read
           and it's waiting for more, the timeout will NOT cancel the
           operation. Set to None for no timeout
        """

        # Ensure it is not cancelled at first, so we can enter the loop
        self.cancelled.clear()

        # Set the starting time so we can
        # calculate whether the timeout should fire
        start_time = datetime.now() if timeout is not None else None

        with BufferedWriter(BytesIO(), buffer_size=size) as buffer:
            bytes_left = size
            while bytes_left != 0:
                # Only do cancel if no data was read yet
                # Otherwise, carry on reading and finish
                if self.cancelled.is_set() and bytes_left == size:
                    raise ReadCancelledError()

                try:
                    partial = self._socket.recv(bytes_left)
                    if len(partial) == 0:
                        self.close()
                        raise ConnectionResetError(
                            'The server has closed the connection.')

                    buffer.write(partial)
                    bytes_left -= len(partial)

                except BlockingIOError as error:
                    # No data available yet, sleep a bit
                    time.sleep(self.delay)

                    # Check if the timeout finished
                    if timeout is not None:
                        time_passed = datetime.now() - start_time
                        if time_passed > timeout:
                            raise TimeoutError(
                                'The read operation exceeded the timeout.') from error

            # If everything went fine, return the read bytes
            buffer.flush()
            return buffer.raw.getvalue()

    def cancel_read(self):
        """Cancels the read operation IF it hasn't yet
           started, raising a ReadCancelledError"""
        self.cancelled.set()