Socket type is incorrect on Windows

`Socket` is defined as holding a `CInt`, but on Windows `SOCKET` is an unsigned 64 bit value, usually `UINT_PTR`. See [1] and [2] this means we may truncate a valid `SOCKET` to something invalid.

[1] https://sourceforge.net/p/mingw-w64/mingw-w64/ci/master/tree/mingw-w64-headers/include/psdk_inc/_socket_types.h
[2] https://docs.microsoft.com/en-us/windows/win32/winsock/socket-data-type-2