The argument is a HOST-PORT specification for the data port to be used in data connection. There are defaults for both the user and server data ports, and under normal circumstances this command and its reply are not needed. The fields are separated by commas. The response to this command includes the host and port address this server is listening on. The argument specifies the representation type as described in the Section on Data Representation and Storage.
Several types take a second parameter.
If the Format parameter is changed, and later just the first argument is changed, Format then returns to the Non-print default. The argument is a single Telnet character code specifying file structure described in the Section on Data Representation and Storage. The default structure is File. The argument is a single Telnet character code specifying the data transfer modes described in the Section on Transmission Modes. An Internet Encyclopedia 4.1.2.