OnCommandClient specifies the TIdDICTShowEvent event handler used to respond to the DICT CLIENT command, as described in RFC 2229. 

The CLIENT command allows the client to provide information about itself for possible logging and statistical purposes. All clients should send this command after connecting to the server. All DICT servers must implement this command, though, the server doesn't have to do anything with the information provided by the client. 

Applications should assign a procedure to the event handler in order to respond to the DICT command, or the server will return the default message: