FileZilla is an open-source File Transfer Protocol (FTP) software program that works for Windows, Linux and Mac computer systems. This program is used to upload, download, compress and encrypt files. These files are stored on servers that a user can connect to unless the all the connections are open. This condition will return a 10068 error code “Too many users. Server is full,” or “Error 421: Too many users for this IP.”
A series 400 error means that the request sent to the server was not accepted and no action was taken, but the error is temporary. Error 421 often appears alongside other errors like “Server sent disconnect message,” “Type 2 (protocol error)” and “Could not connect to server.” This group of errors caused by a maxed-out server is remedied by logging in later.
There are always two endpoints in an FTP connection: the user and the server. "Too many users" errors are generated on the server end of FileZilla. A connection is open when both sides are properly communicating and half-open when one side is not connecting properly. The server counts both open and half-open connections as users. Once all the connections are used, users are locked out.
FileZilla is optimized for speed so it ignores stalled connections until they time out. Modern servers can handle thousands of connections if configured right, but older servers are limited to a couple of hundred. Contact the server administrator to check the connection limit on the server. When a user’s router or firewall drops a connection, the programs do not always inform the user. These dropped connections add to the tally count while the user’s computer attempts another connection. When servers have a long timeout interval, the faulty connections accumulate until the server refreshes.
By limiting the amount of connections the you make with your computer, you help keep the server from filling up as fast. In FileZilla, open “Site Manager” and create an entry for the desired server. Enter all the connection details. Open the “Transfer Settings” tab and check “Limit number of simultaneous connections.” Enter the maximum number of connections that you want to make to this particular server. Do not use too high a number. Be aware, though, that limiting yourself to one connection will stop you from browsing the server while transferring a file.