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
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。