The FTCHKIP user exit is called when a user attempts to log in
to the FTP server or when a user issues the OPEN subcommand to establish
a new connection. The following information is passed to the exit:
- Client IP address *
- Client port number *
- Server IP address *
- Server port number *
- The socket address structure of the client's control connection
- The socket address structure of the server's control connection
- Session instance identifier
Note: Fields above marked with an asterisk (*) are valid only
for IPv4 addresses, including IPv4-mapped IPv6 addresses.
An installation can use this exit to determine if a particular
IP address or port number is allowed to access the FTP site. If the
connection is denied by the user exit, the following message is sent
to the user:
421 User Exit rejects open for connection