Python - non-blocking socket operations raise BlockingIOError

[Boston Walker]

Calling connect() on a non-blocking socket always raises BlockingIOError, due to the C API call returning ZTS_EINPROGRESS.

Example:

socket.settimeout(60.)
socket.connect(("12.34.56.78", 5678))
> BlockingIOError

When using asynchronous (non-blocking) sockets, EINPROGRESS means that the operation is started and to check back again later before continuing to perform operations on the socket.

As well, calling recv() on a non-blocking socket raises ZTS_EGAIN.

In the Python implementations of connect(), recv(), and other functions, asynchronous operations are blocked on by calling poll() or select() on the socket before returning (see socketmodule.c#L816). So the correct behaviour, at least for the Python bindings, should be:

• Call zts_bsd_connect() (or other operation) and get an error code
• If the error code is EINPROGRESS, EAGAIN, or EALREADY, select() or poll() the socket until the socket is ready for the next operation
• Return no error