> Please don't top-post!
Ok. I'm sorry.

>> After some experimenting I found that libssh2_sftp_write() inside
>> Curl_sftp_send in ssh.c permanently returns LIBSSH2_ERROR_EAGAIN in
libcurl.
> That sounds like a libssh2 bug then? I mean, if the socket reports
writable then certainly it should write at least something?
I could hardly imagine, what difference could be between SFTP servers that
could cause that problem. I sent you problem SFTP account auth data in
private letter (that I sent to daniel_at_haxx.se). Could you please try to
upload some file to that server to see what happens?

>> Another strange thing is that channel->local.window_size is 0 at the
>> moment when it is checked in channel.h (line 1709) and
>> libssh2_packet_read() is called.
> Could that possibly be a separate bug or related to the previous one?
I found it while I was debugging the "curl" tool uploading file to the
problem SFTP. I was surprised that the program tried to send 0 bytes when
input stream sill contains data.

Is this problem easy to repeat for you?
Yes the problem is rather stable.

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