ntrol commands and responses are exchanged across the con- trol connection (see Figure 30.5). Then each of the data records is transferred across Storing a file Control Control Data connection process process Client Server Retrieving a file Retrieving a list Figure 30.4 File transfer. Client Server Client Server Control Control Data transfer Data transfer process process process process Records of file Command exchange Records of file Command exchange Control connection Data connection Figure 30.5 File storage. Fundamentals of EMS, NMS and OSS/BSS the data connection. Finally the connection is terminated by exchanging certain commands and responses. The FTP services can be accessed through user interfaces provided by the operating systems. After receiving the input line from the user, the FTP interface reads it and converts it to the corresponding FTP command. The user must have the user name and password on the remote server in order to use FTP. However, the user does not require having the user name and password to access the files present in some sites. Here the user gives the user name as anonymous and the password as guest. These are anonymous FTPs and only a subset of command is allowed to the anonymous users by certain sites. Anonymous login provides limited user access. A knowledge on the files and subfolders present in each folder in a remote com- puter's file system helps to navigate through the folders. This data is returned on the data socket just like files. The folder listings are received from the server when the client issues a LIST command. The server that is waiting for created data sockets responds to the client request. In Windows, the directory listing style with DOS will be of the format: 08/12/2009 09:18 <DIR> 12/11/2009 08:10 <DIR> presentation 08/24/2009 10:31 <DIR> Program Files 05/14/2009 10:51 <DIR> ringtone 11/12/2009 11:51 114,010 Proposal.pdf 11/04/2009 09:24 AM 32,877 submit.pdf In UNIX FTP servers, the directory listing style will be of the format: rw - rw - 1 user group 0 Aug 24 