mirror of https://github.com/python/cpython
425 lines
12 KiB
ReStructuredText
425 lines
12 KiB
ReStructuredText
.. currentmodule:: asyncio
|
|
|
|
.. _asyncio-streams:
|
|
|
|
++++++++++++++++++++++++
|
|
Streams (high-level API)
|
|
++++++++++++++++++++++++
|
|
|
|
Stream functions
|
|
================
|
|
|
|
.. function:: open_connection(host=None, port=None, \*, loop=None, limit=None, **kwds)
|
|
|
|
A wrapper for :meth:`~BaseEventLoop.create_connection()` returning a (reader,
|
|
writer) pair.
|
|
|
|
The reader returned is a :class:`StreamReader` instance; the writer is
|
|
a :class:`StreamWriter` instance.
|
|
|
|
The arguments are all the usual arguments to
|
|
:meth:`BaseEventLoop.create_connection` except *protocol_factory*; most
|
|
common are positional host and port, with various optional keyword arguments
|
|
following.
|
|
|
|
Additional optional keyword arguments are *loop* (to set the event loop
|
|
instance to use) and *limit* (to set the buffer limit passed to the
|
|
:class:`StreamReader`).
|
|
|
|
(If you want to customize the :class:`StreamReader` and/or
|
|
:class:`StreamReaderProtocol` classes, just copy the code -- there's really
|
|
nothing special here except some convenience.)
|
|
|
|
This function is a :ref:`coroutine <coroutine>`.
|
|
|
|
.. function:: start_server(client_connected_cb, host=None, port=None, \*, loop=None, limit=None, **kwds)
|
|
|
|
Start a socket server, with a callback for each client connected. The return
|
|
value is the same as :meth:`~BaseEventLoop.create_server()`.
|
|
|
|
The *client_connected_cb* parameter is called with two parameters:
|
|
*client_reader*, *client_writer*. *client_reader* is a
|
|
:class:`StreamReader` object, while *client_writer* is a
|
|
:class:`StreamWriter` object. The *client_connected_cb* parameter can
|
|
either be a plain callback function or a :ref:`coroutine function
|
|
<coroutine>`; if it is a coroutine function, it will be automatically
|
|
converted into a :class:`Task`.
|
|
|
|
The rest of the arguments are all the usual arguments to
|
|
:meth:`~BaseEventLoop.create_server()` except *protocol_factory*; most
|
|
common are positional *host* and *port*, with various optional keyword
|
|
arguments following.
|
|
|
|
Additional optional keyword arguments are *loop* (to set the event loop
|
|
instance to use) and *limit* (to set the buffer limit passed to the
|
|
:class:`StreamReader`).
|
|
|
|
This function is a :ref:`coroutine <coroutine>`.
|
|
|
|
.. function:: open_unix_connection(path=None, \*, loop=None, limit=None, **kwds)
|
|
|
|
A wrapper for :meth:`~BaseEventLoop.create_unix_connection()` returning
|
|
a (reader, writer) pair.
|
|
|
|
See :func:`open_connection` for information about return value and other
|
|
details.
|
|
|
|
This function is a :ref:`coroutine <coroutine>`.
|
|
|
|
Availability: UNIX.
|
|
|
|
.. function:: start_unix_server(client_connected_cb, path=None, \*, loop=None, limit=None, **kwds)
|
|
|
|
Start a UNIX Domain Socket server, with a callback for each client connected.
|
|
|
|
See :func:`start_server` for information about return value and other
|
|
details.
|
|
|
|
This function is a :ref:`coroutine <coroutine>`.
|
|
|
|
Availability: UNIX.
|
|
|
|
|
|
StreamReader
|
|
============
|
|
|
|
.. class:: StreamReader(limit=None, loop=None)
|
|
|
|
.. method:: exception()
|
|
|
|
Get the exception.
|
|
|
|
.. method:: feed_eof()
|
|
|
|
Acknowledge the EOF.
|
|
|
|
.. method:: feed_data(data)
|
|
|
|
Feed *data* bytes in the internal buffer. Any operations waiting
|
|
for the data will be resumed.
|
|
|
|
.. method:: set_exception(exc)
|
|
|
|
Set the exception.
|
|
|
|
.. method:: set_transport(transport)
|
|
|
|
Set the transport.
|
|
|
|
.. method:: read(n=-1)
|
|
|
|
Read up to *n* bytes. If *n* is not provided, or set to ``-1``,
|
|
read until EOF and return all read bytes.
|
|
|
|
If the EOF was received and the internal buffer is empty,
|
|
return an empty ``bytes`` object.
|
|
|
|
This method is a :ref:`coroutine <coroutine>`.
|
|
|
|
.. method:: readline()
|
|
|
|
Read one line, where "line" is a sequence of bytes ending with ``\n``.
|
|
|
|
If EOF is received, and ``\n`` was not found, the method will
|
|
return the partial read bytes.
|
|
|
|
If the EOF was received and the internal buffer is empty,
|
|
return an empty ``bytes`` object.
|
|
|
|
This method is a :ref:`coroutine <coroutine>`.
|
|
|
|
.. method:: readexactly(n)
|
|
|
|
Read exactly *n* bytes. Raise an :exc:`IncompleteReadError` if the end of
|
|
the stream is reached before *n* can be read, the
|
|
:attr:`IncompleteReadError.partial` attribute of the exception contains
|
|
the partial read bytes.
|
|
|
|
This method is a :ref:`coroutine <coroutine>`.
|
|
|
|
.. method:: at_eof()
|
|
|
|
Return ``True`` if the buffer is empty and :meth:`feed_eof` was called.
|
|
|
|
|
|
StreamWriter
|
|
============
|
|
|
|
.. class:: StreamWriter(transport, protocol, reader, loop)
|
|
|
|
Wraps a Transport.
|
|
|
|
This exposes :meth:`write`, :meth:`writelines`, :meth:`can_write_eof()`,
|
|
:meth:`write_eof`, :meth:`get_extra_info` and :meth:`close`. It adds
|
|
:meth:`drain` which returns an optional :class:`Future` on which you can
|
|
wait for flow control. It also adds a transport attribute which references
|
|
the :class:`Transport` directly.
|
|
|
|
.. attribute:: transport
|
|
|
|
Transport.
|
|
|
|
.. method:: can_write_eof()
|
|
|
|
Return :const:`True` if the transport supports :meth:`write_eof`,
|
|
:const:`False` if not. See :meth:`WriteTransport.can_write_eof`.
|
|
|
|
.. method:: close()
|
|
|
|
Close the transport: see :meth:`BaseTransport.close`.
|
|
|
|
.. method:: drain()
|
|
|
|
Let the write buffer of the underlying transport a chance to be flushed.
|
|
|
|
The intended use is to write::
|
|
|
|
w.write(data)
|
|
yield from w.drain()
|
|
|
|
When the size of the transport buffer reaches the high-water limit (the
|
|
protocol is paused), block until the size of the buffer is drained down
|
|
to the low-water limit and the protocol is resumed. When there is nothing
|
|
to wait for, the yield-from continues immediately.
|
|
|
|
Yielding from :meth:`drain` gives the opportunity for the loop to
|
|
schedule the write operation and flush the buffer. It should especially
|
|
be used when a possibly large amount of data is written to the transport,
|
|
and the coroutine does not yield-from between calls to :meth:`write`.
|
|
|
|
This method is a :ref:`coroutine <coroutine>`.
|
|
|
|
.. method:: get_extra_info(name, default=None)
|
|
|
|
Return optional transport information: see
|
|
:meth:`BaseTransport.get_extra_info`.
|
|
|
|
.. method:: write(data)
|
|
|
|
Write some *data* bytes to the transport: see
|
|
:meth:`WriteTransport.write`.
|
|
|
|
.. method:: writelines(data)
|
|
|
|
Write a list (or any iterable) of data bytes to the transport:
|
|
see :meth:`WriteTransport.writelines`.
|
|
|
|
.. method:: write_eof()
|
|
|
|
Close the write end of the transport after flushing buffered data:
|
|
see :meth:`WriteTransport.write_eof`.
|
|
|
|
|
|
StreamReaderProtocol
|
|
====================
|
|
|
|
.. class:: StreamReaderProtocol(stream_reader, client_connected_cb=None, loop=None)
|
|
|
|
Trivial helper class to adapt between :class:`Protocol` and
|
|
:class:`StreamReader`. Sublclass of :class:`Protocol`.
|
|
|
|
*stream_reader* is a :class:`StreamReader` instance, *client_connected_cb*
|
|
is an optional function called with (stream_reader, stream_writer) when a
|
|
connection is made, *loop* is the event loop instance to use.
|
|
|
|
(This is a helper class instead of making :class:`StreamReader` itself a
|
|
:class:`Protocol` subclass, because the :class:`StreamReader` has other
|
|
potential uses, and to prevent the user of the :class:`StreamReader` to
|
|
accidentally call inappropriate methods of the protocol.)
|
|
|
|
|
|
IncompleteReadError
|
|
===================
|
|
|
|
.. exception:: IncompleteReadError
|
|
|
|
Incomplete read error, subclass of :exc:`EOFError`.
|
|
|
|
.. attribute:: expected
|
|
|
|
Total number of expected bytes (:class:`int`).
|
|
|
|
.. attribute:: partial
|
|
|
|
Read bytes string before the end of stream was reached (:class:`bytes`).
|
|
|
|
|
|
Stream examples
|
|
===============
|
|
|
|
.. _asyncio-tcp-echo-client-streams:
|
|
|
|
TCP echo client using streams
|
|
-----------------------------
|
|
|
|
TCP echo client using the :func:`asyncio.open_connection` function::
|
|
|
|
import asyncio
|
|
|
|
@asyncio.coroutine
|
|
def tcp_echo_client(message, loop):
|
|
reader, writer = yield from asyncio.open_connection('127.0.0.1', 8888,
|
|
loop=loop)
|
|
|
|
print('Send: %r' % message)
|
|
writer.write(message.encode())
|
|
|
|
data = yield from reader.read(100)
|
|
print('Received: %r' % data.decode())
|
|
|
|
print('Close the socket')
|
|
writer.close()
|
|
|
|
message = 'Hello World!'
|
|
loop = asyncio.get_event_loop()
|
|
loop.run_until_complete(tcp_echo_client(message, loop))
|
|
loop.close()
|
|
|
|
.. seealso::
|
|
|
|
The :ref:`TCP echo client protocol <asyncio-tcp-echo-client-protocol>`
|
|
example uses the :meth:`BaseEventLoop.create_connection` method.
|
|
|
|
|
|
.. _asyncio-tcp-echo-server-streams:
|
|
|
|
TCP echo server using streams
|
|
-----------------------------
|
|
|
|
TCP echo server using the :func:`asyncio.start_server` function::
|
|
|
|
import asyncio
|
|
|
|
@asyncio.coroutine
|
|
def handle_echo(reader, writer):
|
|
data = yield from reader.read(100)
|
|
message = data.decode()
|
|
addr = writer.get_extra_info('peername')
|
|
print("Received %r from %r" % (message, addr))
|
|
|
|
print("Send: %r" % message)
|
|
writer.write(data)
|
|
yield from writer.drain()
|
|
|
|
print("Close the client socket")
|
|
writer.close()
|
|
|
|
loop = asyncio.get_event_loop()
|
|
coro = asyncio.start_server(handle_echo, '127.0.0.1', 8888, loop=loop)
|
|
server = loop.run_until_complete(coro)
|
|
|
|
# Serve requests until CTRL+c is pressed
|
|
print('Serving on {}'.format(server.sockets[0].getsockname()))
|
|
try:
|
|
loop.run_forever()
|
|
except KeyboardInterrupt:
|
|
pass
|
|
|
|
# Close the server
|
|
server.close()
|
|
loop.run_until_complete(server.wait_closed())
|
|
loop.close()
|
|
|
|
.. seealso::
|
|
|
|
The :ref:`TCP echo server protocol <asyncio-tcp-echo-server-protocol>`
|
|
example uses the :meth:`BaseEventLoop.create_server` method.
|
|
|
|
|
|
Get HTTP headers
|
|
----------------
|
|
|
|
Simple example querying HTTP headers of the URL passed on the command line::
|
|
|
|
import asyncio
|
|
import urllib.parse
|
|
import sys
|
|
|
|
@asyncio.coroutine
|
|
def print_http_headers(url):
|
|
url = urllib.parse.urlsplit(url)
|
|
if url.scheme == 'https':
|
|
connect = asyncio.open_connection(url.hostname, 443, ssl=True)
|
|
else:
|
|
connect = asyncio.open_connection(url.hostname, 80)
|
|
reader, writer = yield from connect
|
|
query = ('HEAD {path} HTTP/1.0\r\n'
|
|
'Host: {hostname}\r\n'
|
|
'\r\n').format(path=url.path or '/', hostname=url.hostname)
|
|
writer.write(query.encode('latin-1'))
|
|
while True:
|
|
line = yield from reader.readline()
|
|
if not line:
|
|
break
|
|
line = line.decode('latin1').rstrip()
|
|
if line:
|
|
print('HTTP header> %s' % line)
|
|
|
|
# Ignore the body, close the socket
|
|
writer.close()
|
|
|
|
url = sys.argv[1]
|
|
loop = asyncio.get_event_loop()
|
|
task = asyncio.async(print_http_headers(url))
|
|
loop.run_until_complete(task)
|
|
loop.close()
|
|
|
|
Usage::
|
|
|
|
python example.py http://example.com/path/page.html
|
|
|
|
or with HTTPS::
|
|
|
|
python example.py https://example.com/path/page.html
|
|
|
|
.. _asyncio-register-socket-streams:
|
|
|
|
Register an open socket to wait for data using streams
|
|
------------------------------------------------------
|
|
|
|
Coroutine waiting until a socket receives data using the
|
|
:func:`open_connection` function::
|
|
|
|
import asyncio
|
|
try:
|
|
from socket import socketpair
|
|
except ImportError:
|
|
from asyncio.windows_utils import socketpair
|
|
|
|
@asyncio.coroutine
|
|
def wait_for_data(loop):
|
|
# Create a pair of connected sockets
|
|
rsock, wsock = socketpair()
|
|
|
|
# Register the open socket to wait for data
|
|
reader, writer = yield from asyncio.open_connection(sock=rsock, loop=loop)
|
|
|
|
# Simulate the reception of data from the network
|
|
loop.call_soon(wsock.send, 'abc'.encode())
|
|
|
|
# Wait for data
|
|
data = yield from reader.read(100)
|
|
|
|
# Got data, we are done: close the socket
|
|
print("Received:", data.decode())
|
|
writer.close()
|
|
|
|
# Close the second socket
|
|
wsock.close()
|
|
|
|
loop = asyncio.get_event_loop()
|
|
loop.run_until_complete(wait_for_data(loop))
|
|
loop.close()
|
|
|
|
.. seealso::
|
|
|
|
The :ref:`register an open socket to wait for data using a protocol
|
|
<asyncio-register-socket>` example uses a low-level protocol created by the
|
|
:meth:`BaseEventLoop.create_connection` method.
|
|
|
|
The :ref:`watch a file descriptor for read events
|
|
<asyncio-watch-read-event>` example uses the low-level
|
|
:meth:`BaseEventLoop.add_reader` method to register the file descriptor of a
|
|
socket.
|
|
|