传输和协议 ¶

传输层次结构 ¶

class asyncio. BaseTransport ¶

Base class for all transports. Contains methods that all asyncio transports share.

class asyncio. WriteTransport ( BaseTransport ) ¶

A base transport for write-only connections.

实例化的 WriteTransport class are returned from the loop.connect_write_pipe() event loop method and are also used by subprocess-related methods like loop.subprocess_exec() .

class asyncio. ReadTransport ( BaseTransport ) ¶

A base transport for read-only connections.

实例化的 ReadTransport class are returned from the loop.connect_read_pipe() event loop method and are also used by subprocess-related methods like loop.subprocess_exec() .

class asyncio. Transport ( WriteTransport , ReadTransport ) ¶

Interface representing a bidirectional transport, such as a TCP connection.

The user does not instantiate a transport directly; they call a utility function, passing it a protocol factory and other information necessary to create the transport and protocol.

实例化的 Transport class are returned from or used by event loop methods like loop.create_connection() , loop.create_unix_connection() , loop.create_server() , loop.sendfile() ，等。

class asyncio. DatagramTransport ( BaseTransport ) ¶

A transport for datagram (UDP) connections.

实例化的 DatagramTransport class are returned from the loop.create_datagram_endpoint() event loop method.

class asyncio. SubprocessTransport ( BaseTransport ) ¶

An abstraction to represent a connection between a parent and its child OS process.

实例化的 SubprocessTransport class are returned from event loop methods loop.subprocess_shell() and loop.subprocess_exec() .

基传输 ¶

BaseTransport. close ( ) ¶

Close the transport.

If the transport has a buffer for outgoing data, buffered data will be flushed asynchronously. No more data will be received. After all buffered data is flushed, the protocol’s protocol.connection_lost() method will be called with None as its argument.

BaseTransport. is_closing ( ) ¶

返回 True if the transport is closing or is closed.

BaseTransport. get_extra_info ( name , default=None ) ¶

Return information about the transport or underlying resources it uses.

name is a string representing the piece of transport-specific information to get.

default is the value to return if the information is not available, or if the transport does not support querying it with the given third-party event loop implementation or on the current platform.

For example, the following code attempts to get the underlying socket object of the transport:

sock = transport.get_extra_info('socket')
if sock is not None:
    print(sock.getsockopt(...))
											

Categories of information that can be queried on some transports:

• socket:

  • 'peername' : the remote address to which the socket is connected, result of socket.socket.getpeername() ( None on error)

  • 'socket' : socket.socket instance

  • 'sockname' : the socket’s own address, result of socket.socket.getsockname()

• SSL socket:

  • 'compression' : the compression algorithm being used as a string, or None if the connection isn’t compressed; result of ssl.SSLSocket.compression()

  • 'cipher' : a three-value tuple containing the name of the cipher being used, the version of the SSL protocol that defines its use, and the number of secret bits being used; result of ssl.SSLSocket.cipher()

  • 'peercert' : peer certificate; result of ssl.SSLSocket.getpeercert()

  • 'sslcontext' : ssl.SSLContext instance

  • 'ssl_object' : ssl.SSLObject or ssl.SSLSocket instance

• pipe:

  • 'pipe' : pipe object

• subprocess:

  • 'subprocess' : subprocess.Popen instance

BaseTransport. set_protocol ( protocol ) ¶

Set a new protocol.

Switching protocol should only be done when both protocols are documented to support the switch.

BaseTransport. get_protocol ( ) ¶

Return the current protocol.

只读传输 ¶

ReadTransport. is_reading ( ) ¶

返回 True if the transport is receiving new data.

3.7 版新增。

ReadTransport. pause_reading ( ) ¶

Pause the receiving end of the transport. No data will be passed to the protocol’s protocol.data_received() method until resume_reading() 被调用。

3.7 版改变： The method is idempotent, i.e. it can be called when the transport is already paused or closed.

ReadTransport. resume_reading ( ) ¶

Resume the receiving end. The protocol’s protocol.data_received() method will be called once again if some data is available for reading.

3.7 版改变： The method is idempotent, i.e. it can be called when the transport is already reading.

只写传输 ¶

WriteTransport. abort ( ) ¶

Close the transport immediately, without waiting for pending operations to complete. Buffered data will be lost. No more data will be received. The protocol’s protocol.connection_lost() method will eventually be called with None as its argument.

WriteTransport. can_write_eof ( ) ¶

返回 True if the transport supports write_eof() , False 若不。

WriteTransport. get_write_buffer_size ( ) ¶

Return the current size of the output buffer used by the transport.

WriteTransport. get_write_buffer_limits ( ) ¶

获取 high and low watermarks for write flow control. Return a tuple (low, high) where low and high are positive number of bytes.

使用 set_write_buffer_limits() to set the limits.

3.4.2 版新增。

WriteTransport. set_write_buffer_limits ( high=None , low=None ) ¶

设置 high and low watermarks for write flow control.

These two values (measured in number of bytes) control when the protocol’s protocol.pause_writing() and protocol.resume_writing() methods are called. If specified, the low watermark must be less than or equal to the high watermark. Neither high nor low can be negative.

pause_writing() is called when the buffer size becomes greater than or equal to the high value. If writing has been paused, resume_writing() is called when the buffer size becomes less than or equal to the low 值。

The defaults are implementation-specific. If only the high watermark is given, the low watermark defaults to an implementation-specific value less than or equal to the high watermark. Setting high to zero forces low to zero as well, and causes pause_writing() to be called whenever the buffer becomes non-empty. Setting low to zero causes resume_writing() to be called only once the buffer is empty. Use of zero for either limit is generally sub-optimal as it reduces opportunities for doing I/O and computation concurrently.

使用 get_write_buffer_limits() to get the limits.

WriteTransport. write ( data ) ¶

Write some data bytes to the transport.

This method does not block; it buffers the data and arranges for it to be sent out asynchronously.

WriteTransport. writelines ( list_of_data ) ¶

Write a list (or any iterable) of data bytes to the transport. This is functionally equivalent to calling write() on each element yielded by the iterable, but may be implemented more efficiently.

WriteTransport. write_eof ( ) ¶

Close the write end of the transport after flushing all buffered data. Data may still be received.

此方法可以引发 NotImplementedError if the transport (e.g. SSL) doesn’t support half-closed connections.

数据报传输 ¶

DatagramTransport. sendto ( data , addr=None ) ¶

发送 data bytes to the remote peer given by addr (a transport-dependent target address). If addr is None , the data is sent to the target address given on transport creation.

This method does not block; it buffers the data and arranges for it to be sent out asynchronously.

DatagramTransport. abort ( ) ¶

Close the transport immediately, without waiting for pending operations to complete. Buffered data will be lost. No more data will be received. The protocol’s protocol.connection_lost() method will eventually be called with None as its argument.

子进程传输 ¶

SubprocessTransport. get_pid ( ) ¶

Return the subprocess process id as an integer.

SubprocessTransport. get_pipe_transport ( fd ) ¶

Return the transport for the communication pipe corresponding to the integer file descriptor fd :

• 0 : readable streaming transport of the standard input ( stdin )，或 None if the subprocess was not created with stdin=PIPE

• 1 : writable streaming transport of the standard output ( stdout )，或 None if the subprocess was not created with stdout=PIPE

• 2 : writable streaming transport of the standard error ( stderr )，或 None if the subprocess was not created with stderr=PIPE

• other fd : None

SubprocessTransport. get_returncode ( ) ¶

Return the subprocess return code as an integer or None if it hasn’t returned, which is similar to the subprocess.Popen.returncode 属性。

SubprocessTransport. kill ( ) ¶

杀除子进程。

On POSIX systems, the function sends SIGKILL to the subprocess. On Windows, this method is an alias for terminate() .

另请参阅 subprocess.Popen.kill() .

SubprocessTransport. send_signal ( signal ) ¶

发送 signal number to the subprocess, as in subprocess.Popen.send_signal() .

SubprocessTransport. terminate ( ) ¶

停止子进程。

On POSIX systems, this method sends SIGTERM to the subprocess. On Windows, the Windows API function TerminateProcess() is called to stop the subprocess.

另请参阅 subprocess.Popen.terminate() .

SubprocessTransport. close ( ) ¶

Kill the subprocess by calling the kill() 方法。

If the subprocess hasn’t returned yet, and close transports of stdin , stdout ，和 stderr pipes.

基协议 ¶

class asyncio. BaseProtocol ¶

Base protocol with methods that all protocols share.

class asyncio. Protocol ( BaseProtocol ) ¶

The base class for implementing streaming protocols (TCP, Unix sockets, etc).

class asyncio. BufferedProtocol ( BaseProtocol ) ¶

A base class for implementing streaming protocols with manual control of the receive buffer.

class asyncio. DatagramProtocol ( BaseProtocol ) ¶

The base class for implementing datagram (UDP) protocols.

class asyncio. SubprocessProtocol ( BaseProtocol ) ¶

The base class for implementing protocols communicating with child processes (unidirectional pipes).

BaseProtocol ¶

All asyncio protocols can implement Base Protocol callbacks.

连接回调

Connection callbacks are called on all protocols, exactly once per a successful connection. All other protocol callbacks can only be called between those two methods.

BaseProtocol. connection_made ( transport ) ¶

Called when a connection is made.

transport argument is the transport representing the connection. The protocol is responsible for storing the reference to its transport.

BaseProtocol. connection_lost ( exc ) ¶

Called when the connection is lost or closed.

The argument is either an exception object or None . The latter means a regular EOF is received, or the connection was aborted or closed by this side of the connection.

流控件回调

Flow control callbacks can be called by transports to pause or resume writing performed by the protocol.

See the documentation of the set_write_buffer_limits() method for more details.

BaseProtocol. pause_writing ( ) ¶

Called when the transport’s buffer goes over the high watermark.

BaseProtocol. resume_writing ( ) ¶

Called when the transport’s buffer drains below the low watermark.

If the buffer size equals the high watermark, pause_writing() is not called: the buffer size must go strictly over.

Conversely, resume_writing() is called when the buffer size is equal or lower than the low watermark. These end conditions are important to ensure that things go as expected when either mark is zero.

流协议 ¶

Event methods, such as loop.create_server() , loop.create_unix_server() , loop.create_connection() , loop.create_unix_connection() , loop.connect_accepted_socket() , loop.connect_read_pipe() ，和 loop.connect_write_pipe() accept factories that return streaming protocols.

Protocol. data_received ( data ) ¶

Called when some data is received. data is a non-empty bytes object containing the incoming data.

Whether the data is buffered, chunked or reassembled depends on the transport. In general, you shouldn’t rely on specific semantics and instead make your parsing generic and flexible. However, data is always received in the correct order.

The method can be called an arbitrary number of times while a connection is open.

不管怎样， protocol.eof_received() is called at most once. Once eof_received() is called, data_received() is not called anymore.

Protocol. eof_received ( ) ¶

Called when the other end signals it won’t send any more data (for example by calling transport.write_eof() , if the other end also uses asyncio).

This method may return a false value (including None ), in which case the transport will close itself. Conversely, if this method returns a true value, the protocol used determines whether to close the transport. Since the default implementation returns None , it implicitly closes the connection.

Some transports, including SSL, don’t support half-closed connections, in which case returning true from this method will result in the connection being closed.

State machine:

start -> connection_made
    [-> data_received]*
    [-> eof_received]?
-> connection_lost -> end
									

缓冲流协议 ¶

Buffered Protocols can be used with any event loop method that supports 流协议 .

BufferedProtocol implementations allow explicit manual allocation and control of the receive buffer. Event loops can then use the buffer provided by the protocol to avoid unnecessary data copies. This can result in noticeable performance improvement for protocols that receive big amounts of data. Sophisticated protocol implementations can significantly reduce the number of buffer allocations.

The following callbacks are called on BufferedProtocol 实例：

BufferedProtocol. get_buffer ( sizehint ) ¶

Called to allocate a new receive buffer.

sizehint is the recommended minimum size for the returned buffer. It is acceptable to return smaller or larger buffers than what sizehint suggests. When set to -1, the buffer size can be arbitrary. It is an error to return a buffer with a zero size.

get_buffer() must return an object implementing the 缓冲协议 .

BufferedProtocol. buffer_updated ( nbytes ) ¶

Called when the buffer was updated with the received data.

nbytes is the total number of bytes that were written to the buffer.

BufferedProtocol. eof_received ( ) ¶

See the documentation of the protocol.eof_received() 方法。

get_buffer() can be called an arbitrary number of times during a connection. However, protocol.eof_received() is called at most once and, if called, get_buffer() and buffer_updated() won’t be called after it.

State machine:

start -> connection_made
    [-> get_buffer
        [-> buffer_updated]?
    ]*
    [-> eof_received]?
-> connection_lost -> end
									

数据报协议 ¶

Datagram Protocol instances should be constructed by protocol factories passed to the loop.create_datagram_endpoint() 方法。

DatagramProtocol. datagram_received ( data , addr ) ¶

Called when a datagram is received. data is a bytes object containing the incoming data. addr is the address of the peer sending the data; the exact format depends on the transport.

DatagramProtocol. error_received ( exc ) ¶

Called when a previous send or receive operation raises an OSError . exc 是 OSError 实例。

This method is called in rare conditions, when the transport (e.g. UDP) detects that a datagram could not be delivered to its recipient. In many conditions though, undeliverable datagrams will be silently dropped.

子进程协议 ¶

Subprocess Protocol instances should be constructed by protocol factories passed to the loop.subprocess_exec() and loop.subprocess_shell() 方法。

SubprocessProtocol. pipe_data_received ( fd , data ) ¶

Called when the child process writes data into its stdout or stderr pipe.

fd is the integer file descriptor of the pipe.

data is a non-empty bytes object containing the received data.

SubprocessProtocol. pipe_connection_lost ( fd , exc ) ¶

Called when one of the pipes communicating with the child process is closed.

fd is the integer file descriptor that was closed.

SubprocessProtocol. process_exited ( ) ¶

Called when the child process has exited.

TCP 回显服务器 ¶

Create a TCP echo server using the loop.create_server() method, send back received data, and close the connection:

import asyncio
class EchoServerProtocol(asyncio.Protocol):
    def connection_made(self, transport):
        peername = transport.get_extra_info('peername')
        print('Connection from {}'.format(peername))
        self.transport = transport
    def data_received(self, data):
        message = data.decode()
        print('Data received: {!r}'.format(message))
        print('Send: {!r}'.format(message))
        self.transport.write(data)
        print('Close the client socket')
        self.transport.close()
async def main():
    # Get a reference to the event loop as we plan to use
    # low-level APIs.
    loop = asyncio.get_running_loop()
    server = await loop.create_server(
        lambda: EchoServerProtocol(),
        '127.0.0.1', 8888)
    async with server:
        await server.serve_forever()
asyncio.run(main())
									

TCP 回显客户端 ¶

TCP 回显客户端使用 loop.create_connection() method, sends data, and waits until the connection is closed:

import asyncio
class EchoClientProtocol(asyncio.Protocol):
    def __init__(self, message, on_con_lost):
        self.message = message
        self.on_con_lost = on_con_lost
    def connection_made(self, transport):
        transport.write(self.message.encode())
        print('Data sent: {!r}'.format(self.message))
    def data_received(self, data):
        print('Data received: {!r}'.format(data.decode()))
    def connection_lost(self, exc):
        print('The server closed the connection')
        self.on_con_lost.set_result(True)
async def main():
    # Get a reference to the event loop as we plan to use
    # low-level APIs.
    loop = asyncio.get_running_loop()
    on_con_lost = loop.create_future()
    message = 'Hello World!'
    transport, protocol = await loop.create_connection(
        lambda: EchoClientProtocol(message, on_con_lost),
        '127.0.0.1', 8888)
    # Wait until the protocol signals that the connection
    # is lost and close the transport.
    try:
        await on_con_lost
    finally:
        transport.close()
asyncio.run(main())
									

UDP 回显服务器 ¶

UDP 回显服务器，使用 loop.create_datagram_endpoint() 方法，发回收到数据：

import asyncio
class EchoServerProtocol:
    def connection_made(self, transport):
        self.transport = transport
    def datagram_received(self, data, addr):
        message = data.decode()
        print('Received %r from %s' % (message, addr))
        print('Send %r to %s' % (message, addr))
        self.transport.sendto(data, addr)
async def main():
    print("Starting UDP server")
    # Get a reference to the event loop as we plan to use
    # low-level APIs.
    loop = asyncio.get_running_loop()
    # One protocol instance will be created to serve all
    # client requests.
    transport, protocol = await loop.create_datagram_endpoint(
        lambda: EchoServerProtocol(),
        local_addr=('127.0.0.1', 9999))
    try:
        await asyncio.sleep(3600)  # Serve for 1 hour.
    finally:
        transport.close()
asyncio.run(main())
									

UDP 回显客户端 ¶

UDP 回显客户端，使用 loop.create_datagram_endpoint() method, sends data and closes the transport when it receives the answer:

import asyncio
class EchoClientProtocol:
    def __init__(self, message, on_con_lost):
        self.message = message
        self.on_con_lost = on_con_lost
        self.transport = None
    def connection_made(self, transport):
        self.transport = transport
        print('Send:', self.message)
        self.transport.sendto(self.message.encode())
    def datagram_received(self, data, addr):
        print("Received:", data.decode())
        print("Close the socket")
        self.transport.close()
    def error_received(self, exc):
        print('Error received:', exc)
    def connection_lost(self, exc):
        print("Connection closed")
        self.on_con_lost.set_result(True)
async def main():
    # Get a reference to the event loop as we plan to use
    # low-level APIs.
    loop = asyncio.get_running_loop()
    on_con_lost = loop.create_future()
    message = "Hello World!"
    transport, protocol = await loop.create_datagram_endpoint(
        lambda: EchoClientProtocol(message, on_con_lost),
        remote_addr=('127.0.0.1', 9999))
    try:
        await on_con_lost
    finally:
        transport.close()
asyncio.run(main())
									

连接现有套接字 ¶

等待直到套接字接收数据使用 loop.create_connection() 方法采用协议：

import asyncio
import socket
class MyProtocol(asyncio.Protocol):
    def __init__(self, on_con_lost):
        self.transport = None
        self.on_con_lost = on_con_lost
    def connection_made(self, transport):
        self.transport = transport
    def data_received(self, data):
        print("Received:", data.decode())
        # We are done: close the transport;
        # connection_lost() will be called automatically.
        self.transport.close()
    def connection_lost(self, exc):
        # The socket has been closed
        self.on_con_lost.set_result(True)
async def main():
    # Get a reference to the event loop as we plan to use
    # low-level APIs.
    loop = asyncio.get_running_loop()
    on_con_lost = loop.create_future()
    # Create a pair of connected sockets
    rsock, wsock = socket.socketpair()
    # Register the socket to wait for data.
    transport, protocol = await loop.create_connection(
        lambda: MyProtocol(on_con_lost), sock=rsock)
    # Simulate the reception of data from the network.
    loop.call_soon(wsock.send, 'abc'.encode())
    try:
        await protocol.on_con_lost
    finally:
        transport.close()
        wsock.close()
asyncio.run(main())
									

loop.subprocess_exec() 和 SubprocessProtocol ¶

An example of a subprocess protocol used to get the output of a subprocess and to wait for the subprocess exit.

子进程的创建通过 loop.subprocess_exec() 方法：

import asyncio
import sys
class DateProtocol(asyncio.SubprocessProtocol):
    def __init__(self, exit_future):
        self.exit_future = exit_future
        self.output = bytearray()
    def pipe_data_received(self, fd, data):
        self.output.extend(data)
    def process_exited(self):
        self.exit_future.set_result(True)
async def get_date():
    # Get a reference to the event loop as we plan to use
    # low-level APIs.
    loop = asyncio.get_running_loop()
    code = 'import datetime; print(datetime.datetime.now())'
    exit_future = asyncio.Future(loop=loop)
    # Create the subprocess controlled by DateProtocol;
    # redirect the standard output into a pipe.
    transport, protocol = await loop.subprocess_exec(
        lambda: DateProtocol(exit_future),
        sys.executable, '-c', code,
        stdin=None, stderr=None)
    # Wait for the subprocess exit using the process_exited()
    # method of the protocol.
    await exit_future
    # Close the stdout pipe.
    transport.close()
    # Read the output which was collected by the
    # pipe_data_received() method of the protocol.
    data = bytes(protocol.output)
    return data.decode('ascii').rstrip()
date = asyncio.run(get_date())
print(f"Current date: {date}")
									

另请参阅 相同范例 使用高级 API 编写。