SdoClient.download: allow block transfer mode

[dentoyan]

Allow large file transfer when using download. Block transfer mode is correctly implemented.
The block_transfer argument must be set to True for the open method. This will speed up the transfer significantly.

[sveinse]

Hi! What is the question here? Isn't the block_transfer mode of open() working on downloads? Neither upload() nor download() of SdoClient use block transfer mode, you have to call open() manually.

[dentoyan]

Please review my commit 07d82a6

[acolomb]

Sorry, I don't get what the intention is here, either. You want SdoClient.download() to default to block transfer mode? That doesn't make sense in the vast majority of use cases. And for those where it does, we have a solution by using open() directly from your application code.

[sveinse]

What PR is this from?

Can I maybe suggest to add block_transfer: bool = False as an additional argument to SdoClient.upload() and SdoClient.download().? If you do , please remember that the prototypes in SdoBase.upload() and SdoBase.download() must be updated too.

[dentoyan]

Adding an additional argument is a good idea.
Block Transfer: multiple segments are confirmed by only 1 confirm message.
On Initiate Block Download command the server returns the number of segments per block. So the client can select the optimal transfer mode.