Host is a Published property in TIdFTP, and represents the IP address or host name for the remote FTP server. 

Values in the Host and Port properties are used in the Connect method to establish and initialize the connection used as the control channel for the FTP client session. When ProxySettings contains ProxyType and Host values, the Host and Port properties in ProxySettings are used to open the initial connection for the FTP client session. After the control channel connection is opened, the Host and Port properties revert to their previous values. 

Set values in the Host, Port, and ProxySettings properties prior to calling the Connect method. 

Use Port to specifiy the port number for the FTP client session.

Port 

ProxySettings 

Connect