In file Modules/socketmodule.c, sock_send/sock_sendall use int to keep array length need be sent and has sent.

Related issue : issue18100 . Seems this was fixed in 3.x .

Can we fix it in 2.7?

2.7 is in bugfix mode, but I have created a PR (not yet completed, need to be tested with real unittest).

Could you try my PR and why not produce a script for the tests.

Thank you.

Thanks for your contribute! I just have read your PR on github.
Because I am not familiar about how to contribute a patch, I doubt it's reasonable to write a test which will consuming more than 2GB memory space? Because if write a test to cover this case, we will build a string larger than 2GB, and use socket to send it. Dose the machine running tests have enough memory resource?

Hi @kmiku7, it's possible to write tests that use a large amount of memory and to run them only when asked to with bigmemtest: https://docs.python.org/3/library/test.html#test.support.bigmemtest

There is some tests that use it in the codebase like https://github.com/python/cpython/blob/1561703a78849ac3511055590d9d1bd2c62a2072/Lib/test/test_bz2.py#L646-L647

Creating a large string and sending it through a socket should be ok if you mark the test with this decorator.

@kmiku7: Did you find this issue in production or while testing Python? Or did you spot the idea while reading Python source code?

> Because I am not familiar about how to contribute a patch, I doubt it's reasonable to write a test which will consuming more than 2GB memory space? Because if write a test to cover this case, we will build a string larger than 2GB, and use socket to send it. Dose the machine running tests have enough memory resource?

Most computers have at least 4 GB of memory. It would be possible to write a "bigmem" test which build a string longer than 2 GiB, send it and check the received length, but I'm not sure that it's worth it: there is no such test in the master branch.

New changeset f70b884ad70e2ce762842ae469f88bd48fe13998 by Victor Stinner (Stéphane Wirtel) in branch '2.7':
bpo-36337: socket.send()/sendall() use Py_ssize_t (GH-12397)
https://github.com/python/cpython/commit/f70b884ad70e2ce762842ae469f88bd48fe13998

Thanks Stéphane for the quick fix, I merged your PR. Thanks kmiku7 for your bug report.

Until the next Python 2.7 version is released, you can use Python 3 which is already fixed ;-)