A final post on this: I contacted the server-side, they checked and couldn't find anything wrong with the settings or provide a suggestion on changing something on DOpus - everything seems regular. So, I'll have to use another FTP client.
Thank you. Yes, three other SFTP clients achieve full speed on the same server (as does DOPus 11/12 in standard FTP mode). DOpus SFTP reaches about 40% of that speed. This is on upload only - download is ok.
Possibly a network buffer/window size or latency situation that our code isn't dealing with as well as the others. Unfortunately, I do not think those things are adjustable for SFTP at the moment.
(There is Preferences / Miscellaneous / Advanced: ftp_copy_buffer_size, but I am pretty sure it only affects FTP and not SFTP.)
Sometimes firewall software treats different processes differently, but it seems fairly unlikely it would be slowing down SFTP and not FTP in the same process, and only in one direction, in one process.
I have been having this issue with dopus for many years and so have others. They know about it and have not done anything I just use WinSCP now.
Some of the other threads:
2014: Very slow FTP
2015: Sftp is very slow
I had this problems for years too (I bought all versions since 9). Using SFTP upload, DO is really slow compared to other programs. Problem is on local LAN connections as well on remote WAN connections. Even if with small files (20-30 megs) the upload speed is slow sometimes ten times slowers than other programs (i.e WinSCP or Filezilla).
I tested the shareware version 12 of DO (I still have to buy the upgraded license) but it's still slow.
Unfortunately, the problem remains in the latest 12.2 version. SFTP downloads seems to be ok here (multiple connection and/or segment downloading would be better but that's not the issue here), but SFTP upload speed is problematic.
I don't know either, that's why I'm asking here @Leo
Per thread title, this is SFTP. Nothing special about the server, in FileZilla I just put in the IP and user/pass and it works fine. I'm talking about single thread speeds, not multi-thread.
If I can't get DOpus to upload faster than half a MB/sec, the advanced FTP feature isn't much use to me. I'd love to figure out why DOpus is slow when FileZilla and other clients to the server are having no speed issues via SSH/SFTP.
Not sure if this would help, or whether developer's are aware of the TGPuttyLib SFTP library, but it may offer improved SFTP speeds.As @Leo is getting fast speeds though, it would be useful to know why some people aren't. As @AmigaOpus says, maybe more server details plus logging info might help debug the problem.