42 lines
1.6 KiB
Python
42 lines
1.6 KiB
Python
# echo-server.py
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import trio
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from itertools import count
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# Port is arbitrary, but:
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# - must be in between 1024 and 65535
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# - can't be in use by some other program on your computer
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# - must match what we set in our echo client
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PORT = 8081
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CONNECTION_COUNTER = count()
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async def echo_server(server_stream):
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# Assign each connection a unique number to make our debug prints easier
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# to understand when there are multiple simultaneous connections.
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ident = next(CONNECTION_COUNTER)
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print(f"echo_server {ident}: started")
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try:
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async for data in server_stream:
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print(f"echo_server {ident}: received data {data!r}")
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await server_stream.send_all(data)
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print(f"echo_server {ident}: connection closed")
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# FIXME: add discussion of (Base)ExceptionGroup to the tutorial, and use
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# exceptiongroup.catch() here. (Not important in this case, but important
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# if the server code uses nurseries internally.)
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except Exception as exc:
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# Unhandled exceptions will propagate into our parent and take
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# down the whole program. If the exception is KeyboardInterrupt,
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# that's what we want, but otherwise maybe not...
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print(f"echo_server {ident}: crashed: {exc!r}")
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async def main():
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await trio.serve_tcp(echo_server, PORT)
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# We could also just write 'trio.run(trio.serve_tcp, echo_server, PORT)', but real
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# programs almost always end up doing other stuff too and then we'd have to go
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# back and factor it out into a separate function anyway. So it's simplest to
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# just make it a standalone function from the beginning.
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trio.run(main) |