FTP server application data format for the control connection

The FTP server control connection is established when the FTP daemon accepts an incoming connection on its listening socket (the connection is passed from the daemon to the server). Table 1 shows the format of the application data set by the FTP server for its control connection socket.

Table 1. FTP server application data format for the control connection
Bytes	Description
1 - 8	The component ID of FTP, EZAFTP0S
9	Blank
10	The FTP connection: C Control connection
11	Blank
12 - 20	The user name used to log into FTP, padded to the right with blanks. This field might be blank if the user is not logged into 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; Bank otherwise. T TLS managed by AT-TLS G GSSAPI F TLS managed by FTP
24, 25	The security level if security method is TLS and the handshake has completed; blank otherwise (see Note). S2 SSLv2 S3 SSLv3 T1 TLSv1 11 TLSv1.1 12 TLSv1.2
26,27	The security cipher used if the security method is TLS and the handshake has completed; blank otherwise (see Note). If the value is 4X, the security cipher must be obtained from offset 29.
28	Blank
29 - 32	The security cipher that is used if the security method is TLS that is managed by FTP or AT-TLS; blank otherwise (see Note).
33 - 40	Reserved blank
Note: This value is negotiated during the TLS handshake. Another TLS handshake can occur at any time. When the FTP server next updates the APPLDATA, this value might change.