I tried to enable and disable TLS, the ports are open on the server router and firewall.
I noticed that FTP authorization creates a load of 100% cpu, 2 cores, and lasts about 3 seconds.
filezilla uses 10 threads at the same time. When transferring 10 files at once, the task fails.
By limiting concurrent streams to 5, the problem disappears.
Why is there such a heavy load on the CPU during authorization, and authorization takes 3 seconds?
Centos 7, passive mode
16:09:33 Status: Connecting to ...:21...
16:09:33 Status: Connection established, waiting for welcome message...
16:09:33 Status: Plain FTP is insecure. Please switch to FTP over TLS.
16:09:35 Status: Logged in
16:09:35 Status: Retrieving directory listing...
16:09:35 Status: Directory listing of "/" successful
16:10:18 Status: Connecting to ...:21...
16:10:18 Status: Connecting to ...:21...
16:10:18 Status: Connecting to ...:21...
16:10:18 Status: Connection established, waiting for welcome message...
16:10:18 Status: Connecting to ...:21...
16:10:18 Status: Connection established, waiting for welcome message...
16:10:18 Status: Connecting to ...:21...
16:10:18 Status: Connection established, waiting for welcome message...
16:10:18 Status: Connecting to ...:21...
16:10:18 Status: Connection established, waiting for welcome message...
16:10:18 Status: Connecting to ...:21...
16:10:18 Status: Connection established, waiting for welcome message...
16:10:18 Status: Connecting to ...:21...
16:10:18 Status: Connection established, waiting for welcome message...
16:10:18 Status: Connecting to ...:21...
16:10:18 Status: Connection established, waiting for welcome message...
16:10:18 Status: Connecting to ...:21...
16:10:18 Status: Connection established, waiting for welcome message...
16:10:18 Status: Connection established, waiting for welcome message...
16:10:18 Status: Connection established, waiting for welcome message...
16:10:18 Status: Plain FTP is insecure. Please switch to FTP over TLS.
16:10:18 Status: Plain FTP is insecure. Please switch to FTP over TLS.
16:10:18 Status: Plain FTP is insecure. Please switch to FTP over TLS.
16:10:18 Status: Plain FTP is insecure. Please switch to FTP over TLS.
16:10:18 Status: Plain FTP is insecure. Please switch to FTP over TLS.
16:10:18 Status: Plain FTP is insecure. Please switch to FTP over TLS.
16:10:18 Status: Plain FTP is insecure. Please switch to FTP over TLS.
16:10:18 Status: Plain FTP is insecure. Please switch to FTP over TLS.
16:10:18 Status: Plain FTP is insecure. Please switch to FTP over TLS.
16:10:18 Status: Plain FTP is insecure. Please switch to FTP over TLS.
16:10:18 Command: USER TBm4zfehXbGRRisC
16:10:18 Response: 331 User TBm4zfehXbGRRisC OK. Password required
16:10:18 Command: PASS ****************
16:10:28 Error: Connection timed out after 10 seconds of inactivity
16:10:28 Error: Could not connect to server
16:10:18 Command: USER TBm4zfehXbGRRisC
16:10:18 Response: 331 User TBm4zfehXbGRRisC OK. Password required
16:10:18 Command: PASS ****************
16:10:28 Error: Connection timed out after 10 seconds of inactivity
16:10:28 Error: Could not connect to server
16:10:18 Command: USER TBm4zfehXbGRRisC
16:10:18 Response: 331 User TBm4zfehXbGRRisC OK. Password required
16:10:18 Command: PASS ****************
16:10:28 Error: Connection timed out after 10 seconds of inactivity
16:10:28 Error: Could not connect to server
16:10:18 Command: USER TBm4zfehXbGRRisC
16:10:18 Response: 331 User TBm4zfehXbGRRisC OK. Password required
16:10:18 Command: PASS ****************
16:10:28 Error: Connection timed out after 10 seconds of inactivity
16:10:28 Error: Could not connect to server
16:10:18 Command: USER TBm4zfehXbGRRisC
16:10:18 Response: 331 User TBm4zfehXbGRRisC OK. Password required
16:10:18 Command: PASS ****************
16:10:28 Error: Connection timed out after 10 seconds of inactivity
16:10:28 Error: Could not connect to server
16:10:18 Command: USER TBm4zfehXbGRRisC
16:10:18 Response: 331 User TBm4zfehXbGRRisC OK. Password required
16:10:18 Command: PASS ****************
16:10:28 Error: Connection timed out after 10 seconds of inactivity
16:10:28 Error: Could not connect to server
16:10:18 Command: USER TBm4zfehXbGRRisC
16:10:18 Response: 331 User TBm4zfehXbGRRisC OK. Password required
16:10:18 Command: PASS ****************
16:10:28 Error: Connection timed out after 10 seconds of inactivity
16:10:28 Error: Could not connect to server
16:10:18 Command: USER TBm4zfehXbGRRisC
16:10:18 Response: 331 User TBm4zfehXbGRRisC OK. Password required
16:10:18 Command: PASS ****************
16:10:28 Error: Connection timed out after 10 seconds of inactivity
16:10:28 Error: Could not connect to server
16:10:18 Command: USER TBm4zfehXbGRRisC
16:10:18 Response: 331 User TBm4zfehXbGRRisC OK. Password required
16:10:18 Command: PASS ****************
16:10:28 Error: Connection timed out after 10 seconds of inactivity
16:10:28 Error: Could not connect to server
16:10:18 Command: USER TBm4zfehXbGRRisC
16:10:18 Response: 331 User TBm4zfehXbGRRisC OK. Password required
16:10:18 Command: PASS ****************
16:10:28 Error: Connection timed out after 10 seconds of inactivity
16:10:28 Error: Could not connect to server