I've talked to ar1s about this before, I have a problem with the connector interface. After a character has been sent, nothing is transmitted anymore. I can reproduce the problem on Windows and Linux.
As an example I changed the "samplesshd-cb.c" from the examples folder.
When the user has authenticated, a connection to the local echo service will be established ( should also be enabled for this example ). Then the connector interface should be used to transfer all data from the channel to the socket and all data from the socket to the channel.
But this does not work correctly.
I can excluded a bug in the windows poll emulation, because I could reproduce the behavior under linux ( Debian 9.5 ).
Strangely enough, everything seems to work fine if you use the connector interface for the client side ( as in the example "libssh\examples\ssh_client.c" ).
If I want to use the connector interface for the server side, only the first data block is transferred, then nothing more.