Initial Commit

triotest1/echo_server.py

@@ -0,0 +1,42 @@
+# echo-server.py
+
+import trio
+from itertools import count
+# Port is arbitrary, but:
+# - must be in between 1024 and 65535
+# - can't be in use by some other program on your computer
+# - must match what we set in our echo client
+PORT = 8081
+
+CONNECTION_COUNTER = count()
+
+
+async def echo_server(server_stream):
+    # Assign each connection a unique number to make our debug prints easier
+    # to understand when there are multiple simultaneous connections.
+    ident = next(CONNECTION_COUNTER)
+    print(f"echo_server {ident}: started")
+    try:
+        async for data in server_stream:
+            print(f"echo_server {ident}: received data {data!r}")
+            await server_stream.send_all(data)
+        print(f"echo_server {ident}: connection closed")
+    # FIXME: add discussion of (Base)ExceptionGroup to the tutorial, and use
+    # exceptiongroup.catch() here. (Not important in this case, but important
+    # if the server code uses nurseries internally.)
+    except Exception as exc:
+        # Unhandled exceptions will propagate into our parent and take
+        # down the whole program. If the exception is KeyboardInterrupt,
+        # that's what we want, but otherwise maybe not...
+        print(f"echo_server {ident}: crashed: {exc!r}")
+
+
+async def main():
+    await trio.serve_tcp(echo_server, PORT)
+
+
+# We could also just write 'trio.run(trio.serve_tcp, echo_server, PORT)', but real
+# programs almost always end up doing other stuff too and then we'd have to go
+# back and factor it out into a separate function anyway. So it's simplest to
+# just make it a standalone function from the beginning.
+trio.run(main)