asyncio不会通过tcp发送整个图像数据

时间:2018-06-11 01:33:13

标签: python python-3.x tcp python-asyncio python-sockets

我正在尝试使用带有TCP协议的asyncio将映像从本地计算机发送到云中的计算机。有时我会发送整个图像,有时只会发送部分图像。

客户端代码

import os
os.environ['PYTHONASYNCIODEBUG'] = '1'
import asyncio
import logging

logging.basicConfig(level=logging.ERROR)
async def tcp_echo_client(data, loop):
    reader, writer = await asyncio.open_connection(<ip_addr>, <port>,
                                                   loop=loop)
    print('Sending data of size: %r' % str(len(data)))
    writer.write(data)
    await writer.drain()
    #print("Message: %r" %(data))
    print(type(data))
    print('Close the socket')
    writer.write_eof()
    writer.close()

with open('sendpic0.jpg','rb') as f:
    data=f.read()
loop = asyncio.get_event_loop()
loop.run_until_complete(tcp_echo_client(data, loop))
loop.close()

服务器代码:

import os
os.environ['PYTHONASYNCIODEBUG'] = '1'
import asyncio
import logging

logging.basicConfig(level=logging.ERROR)

async def handle_echo(reader, writer):

    data = await reader.read()
    addr = writer.get_extra_info('peername')
    #print("Received %r from %r" % (message, addr))
    print("Length of data recieved: %r" % (str(len(data))))
    #with open('recvpic0.jpg','wb') as f:
    #    f.write(data)
    print("Close the client socket")
    writer.close()
    #print("Message: %r" %(data))
    print("Received data of length: %r" %(str(len(data))))


loop = asyncio.get_event_loop()
data=b''
coro = asyncio.start_server(handle_echo, '', <port_number>, loop=loop)
server = loop.run_until_complete(coro)
print("Received data of length: %r" %(str(len(data))))
# 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()

我没有故意提供IP地址和端口号,但这不重要。

这是输出:

服务器输出

Received data of length: '0'
Serving on ('0.0.0.0', 50001)

Length of data recieved: '249216'
Close the client socket
Received data of length: '249216'                                                                              

Length of data recieved: '250624'       
Close the client socket                                                                          
Received data of length: '250624'

Length of data recieved: '256403'                                                                              
Close the client socket                                                  
Received data of length: '256403'                                                                                              

客户端输出

$ python client.py       
Sending data of size: '256403' 
Close the socket
$ python client.py
<class 'bytes'>                                                                               
Close the socket                                                                              
$ python client.py       
Sending data of size: '256403'                                                                
<class 'bytes'>                                                                               
Close the socket                                                                              

我正在使用Python 3.6。

我不知道我是否应该拥有检查机制或以块的形式发送数据?我会假设所有这些都会在读取函数下自动发生。

我调整了此网站的代码:http://asyncio.readthedocs.io/en/latest/tcp_echo.html

1 个答案:

答案 0 :(得分:3)

这看起来像是in this article中详细描述的关闭编写器错误。

简而言之,writer.close不是协程,因此您不能等待接近实际将数据从asyncio的缓冲区刷新到操作系统。在writer.drain()之前等待close()并没有帮助,因为它只会暂停直到后台写入将缓冲区大小减小到“低水印”为止,而不是-正如人们所期望的那样-直到缓冲区被清空。

更新:从2018年6月发布的Python 3.7开始,简单的修复方法是在tcp_echo_writer的末尾等待writer.wait_closed()


在最初编写答案时,唯一可用的解决方法是复制asyncio.open_connection的实现(听起来不那么糟糕,因为它是一种便捷功能),并向{{ 1}}。这将使transport.set_write_buffer_limits(0)实际上等待将所有数据写入操作系统(引用的文章认为无论如何都是正确的做法!):

await writer.drain()
  

奇怪的是,这样的错误使我们隐藏在主要的asyncio库中。

我怀疑大多数人看不到该错误,因为他们使事件循环在执行其他事情时运行了更长的时间,因此在@asyncio.coroutine def fixed_open_connection(host=None, port=None, *, loop=None, limit=65536, **kwds): if loop is None: loop = asyncio.get_event_loop() reader = asyncio.StreamReader(limit=limit, loop=loop) protocol = asyncio.StreamReaderProtocol(reader, loop=loop) transport, _ = yield from loop.create_connection( lambda: protocol, host, port, **kwds) ###### Following line added to fix buffering issues: transport.set_write_buffer_limits(0) ###### writer = asyncio.StreamWriter(transport, protocol, reader, loop) return reader, writer 之后,数据最终被写出,插座已关闭。