https://github.com/python/cpython/commit/21b68a1198fbfada3d3c11576c0f9676a4c... commit: 21b68a1198fbfada3d3c11576c0f9676a4cf5978 branch: 3.12 author: Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com> committer: hauntsaninja <12621235+hauntsaninja@users.noreply.github.com> date: 2024-02-01T00:50:34Z summary: [3.12] gh-111112: Avoid potential confusion in TCP server example. (GH-111113) (#114831) gh-111112: Avoid potential confusion in TCP server example. (GH-111113) Improve misleading TCP server docs and example. socket.recv(), as documented by the Python reference documentation, returns at most `bufsize` bytes, and the underlying TCP protocol means there is no guaranteed correspondence between what is sent by the client and what is received by the server. This conflation could mislead readers into thinking that TCP is datagram-based or has similar semantics, which will likely appear to work for simple cases, but introduce difficult to reproduce bugs. (cherry picked from commit a79a27242f75fc33416d4d135a4a542898d140e5) Co-authored-by: Aidan Holm <alfh@google.com> files: M Doc/library/socketserver.rst diff --git a/Doc/library/socketserver.rst b/Doc/library/socketserver.rst index 5fd213fa613c8d..864b1dadb78562 100644 --- a/Doc/library/socketserver.rst +++ b/Doc/library/socketserver.rst @@ -494,7 +494,7 @@ This is the server side:: def handle(self): # self.request is the TCP socket connected to the client self.data = self.request.recv(1024).strip() - print("{} wrote:".format(self.client_address[0])) + print("Received from {}:".format(self.client_address[0])) print(self.data) # just send back the same data, but upper-cased self.request.sendall(self.data.upper()) @@ -525,8 +525,9 @@ objects that simplify communication by providing the standard file interface):: The difference is that the ``readline()`` call in the second handler will call ``recv()`` multiple times until it encounters a newline character, while the -single ``recv()`` call in the first handler will just return what has been sent -from the client in one ``sendall()`` call. +single ``recv()`` call in the first handler will just return what has been +received so far from the client's ``sendall()`` call (typically all of it, but +this is not guaranteed by the TCP protocol). This is the client side::