The FTP client sent a command to the server. The server rejected the command because the command is not compatible with a command that the client sent to the server earlier in the login session.
503 Command PROT rejected -- PROT not allowed after CCCThe FTP server ignores the specified command.
Contact the system programmer.
If the prior_command value is CCC, it is probable that the user violated the rules established in RFC 4217 for using a TLS-secured session. When the control connection has been cleared, RFC 4217 stipulates that the server must reject certain commands. See RFC 2228 FTP Security Extensions and RFC 4217 Securing FTP with TLS for more information about the correct sequencing of commands during a secured session. Educate the user in the correct use of a secured session. If the prior_command value is not CCC, see RFC 959 File Transfer Protocol for information about correct command sequences during an FTP session. See Related protocol specifications for information about accessing RFCs.
Not applicable.
z/OS® Communications Server TCP/IP: FTP