How to Increase the Maximum FTP Connections per IP in Centova Cast (421 Too Many Connections)

Updated: 8 October 2026 · Applies to: Centova Cast v3 (current release 3.3.4), FileZilla Client 3; per-IP limit behaviour tested with Pure-FTPd 1.0.50 on Debian 13

The FTP error 421 Too many connections (2) from this IP means your FTP program opened more connections than Centova Cast's FTP server allows from one IP address. The number in brackets is the server's limit. The quick fix, which anyone can do, is to set your FTP program to use no more connections than that number. Server owners can also raise the limit in /usr/local/centovacast/etc/cc-ftpd.conf and restart Centova Cast's FTP server.

Why the error appears

According to Centova, its FTP server (cc-ftpd) is a modified Pure-FTPd. Pure-FTPd counts every open connection from the same IP address and refuses new ones above the limit, straight after connecting and before the login. We started a standard Pure-FTPd with a limit of 2 and opened three logins from one address:

connection 1: 230 OK. Current directory is /
connection 2: 230 OK. Current directory is /
connection 3: 421 Too many connections (2) from this IP

With the limit set to 4, the fifth connection got 421 Too many connections (4) from this IP, which confirms that the number in the message is the server's setting. Common reasons for going over it:

• FileZilla's defaults. FileZilla keeps one connection open for browsing and runs up to 2 transfers at once by default, each on its own connection. That is 3 connections, one more than a limit of 2.
• A shared public IP. Several people or computers behind the same office or home router count as one IP address.
• Sessions that did not close cleanly. An old session can keep counting until the server drops it (a standard Pure-FTPd closes idle sessions after 15 minutes).

Fix it in FileZilla (all users)

This is the fix for hosted stream customers, and it needs no server change.

1. Open File › Site Manager and select your Centova Cast site.
2. Open the Transfer Settings tab.
3. Tick Limit number of simultaneous connections and set Maximum number of connections to the number shown in the error (for example 2), or to 1.
4. Click Connect. FileZilla counts its browsing connection in this limit, and with a limit of 1 it sends transfers over the browsing connection.

To change it for every site instead, open Edit › Settings › Transfers and lower Maximum simultaneous transfers to 1. In other FTP programs, look for a similar setting for simultaneous transfers or connections. If the error still appears, disconnect, wait a few minutes for old sessions to close and connect again.

Hosted stream customers who need a higher limit should open a support ticket, because the limit is a server setting.

Raise the limit on your server (root)

On a Centova Cast dedicated server or VPS you can change the limit yourself. According to Centova, cc-ftpd.conf is a small shell script whose values are passed to Pure-FTPd as command-line options.

1. Back up the file:

   cp -a /usr/local/centovacast/etc/cc-ftpd.conf /root/cc-ftpd.conf.bak

2. List the settings it contains:

   grep -n '^FTP_' /usr/local/centovacast/etc/cc-ftpd.conf

3. Look in that output for a line that sets the number of connections allowed per IP address, and raise its value, for example to 4. Setting names differ between Centova Cast builds, so go by what your own file shows. If no such line exists, Centova has described an FTP_OPTIONS setting for passing extra options to Pure-FTPd. Pure-FTPd's per-IP option is -C, so the line would be FTP_OPTIONS="-C 4". Change only one of the two.
4. Restart Centova Cast's FTP server:

   /usr/local/centovacast/centovacast stop-ftp
   /usr/local/centovacast/centovacast start-ftp

   Restarting the whole of Centova Cast with /usr/local/centovacast/centovacast restart also works.
5. Test it. Open more connections than before (for example raise FileZilla's limit for a moment). If the limit is still too low, the 421 message shows the active value. This is the easiest check, because Pure-FTPd hides its options from the process list: in our test ps showed only pure-ftpd (SERVER).

Keep the number modest, such as 3 to 5. Pure-FTPd's manual describes the per-IP limit as an effective protection against denial of service and against one user using up all the bandwidth. If the FTP server does not come back after the change, restore the backup file and start it again.

Related FTP problems

• Cannot connect at all: unable to connect with FTP to upload music.
• Logged in, but the upload fails: errors while uploading to Centova Cast by FTP.
• Many files to upload: compare FTP with the web uploader in FTP or the web-based file uploader.

Official documentation: Centova Cast core files and paths, Controlling Centova Cast.