FTP client application data format for the control connection

An FTP control connection is established when an FTP client logs into an FTP server. Table 1 shows the format of the application data set by the client for its control connection socket.

Table 1. FTP client application data format for the control connection
Bytes	Description
1 - 8	The component ID of FTP, EZAFTP0C
9	Blank
10	The FTP connection: C Control connection
11	Blank
12 - 20	The user name of the FTP client, padded on the right with blanks. This field might be blank if the user is not logged in to the FTP server.
21	Blank
22	Security protection for the connection: C Clear L Clear, but previously was Private or Safe P Private S Safe
23	The security method used for the FTP connection if security protection is either Private or Safe; blank otherwise. T TLS managed by AT-TLS G GSSAPI F TLS managed by FTP
24, 25	The security level if security method is TLS; blank otherwise (see Note). S2 SSLv2 S3 SSLv3 T1 TLSv1 11 TLSv1.1 12 TLSv1.2 13 TLSv1.3
26, 27	The security cipher used if the security method is TLS managed by FTP or AT-TLS; blank otherwise (see Note). If the value is 4X, the security cipher must be obtained from offset 30.
28	Blank
29	SOCKS server connection: D Direct connection; not through a SOCKS server. S Connection through a SOCKS server.
30 - 33	The four byte security cipher that is used if the security method is TLS that is managed by FTP or AT-TLS; blank otherwise (see Note).
34 - 40	Reserved blank
Note: This value is negotiated during the TLS handshake. Another TLS handshake can occur at any time. The value in this record should be considered a snapshot of the current value at the time the FTP client set application data.