Failed to connect to FTP server: 421 Service not available

Symptoms

• During the connection to the FTP server, the following error appears:

  PLESK_INFO: Failed to connect to FTP server: 421 Service not available

• The following error messages can be found in /var/log/messages or in Proftpd debug output (proftpd -nd10):

  CONFIG_TEXT: example.com proftpd[130008] 127.0.0.1: Failed binding to ::, port 21: Address already in use
  example.com proftpd[130008] 127.0.0.1: Check to see if inetd/xinetd, or another proftpd instance, is already using ::, port 21

• In case standalone ProFTPd is in use, port 3303 is mentioned in /var/log/messages:

  CONFIG_TEXT: example.com proftpd[22426]: 0.0.0.0 - Check to see if inetd/xinetd, or another proftpd instance, is already using ::, port 3303

Cause

Another application is using the port 21 or another ProFTPd instance is running on port 3303.

Alternatively, ProFTPd service is stuck.

Resolution

1. Connect to a Plesk server via SSH.

2. Get PID of proftpd service:

   # netstat -putan | grep :3303
   tcp6 0 0 :::3303 :::* LISTEN 4225/proftpd:

3. Kill proftpd service:

   # kill -9 4225

4. Verify that ServerType parameter in /etc/proftpd.conf is set as follows:

   CONFIG_TEXT: ServerType inetd

   Note: In case another server type is specified, delete or comment that line.

5. Restart xinetd service with the following command:

   # service xinetd restart

6. Try to connect to the FTP server again.

   Note: If the issue still appears, apply the solution from this KB article.

Additional Information

• Failed to connect to FTP server: 421 Service not available