FTP Background:

• Uses standard Internet protocols and conventions for file transfer (i.e., use FTP as opposed to creating a custom TCP/IP file transfer protocol).
• The AS/400 may function as either FTP client or FTP server as required.
• For switched (SLIP) connections, allow either party to initiate the dial connection independent of whether the AS/400 is acting as client or server.
Use the same interactive panels as are used for other communications methods.
• Enable automated operations using the same EXTOL commands as for other connection methods.
• Create appropriate log records in the EXTOL system to enable tracking of FTP connections using the same log database and user interface as is presently used for tracking other connections (BISYNC, ASYNC, SNA, file/tape, etc.)

FTP Overview:

The EXTOL system uses a single table-driven communications program for all connection methods other than the pseudo-communications with networks *FILE and *TAPE. These include both switched and non-switched support for SNA (both APPC LU6.2 and SNUF), BISYNC, ASYNC, and X.25. The operating system support for all of these methods is provided through the Intersystem Communications Function (ICF) file mechanism. The TCP/IP protocol is sufficiently different from the other communications methods that IBM decided to provide support not through ICF, but rather through native OS/400 implementations of the various TCP/IP protocols and utilities.

Consequently, the EXTOL implementation of TCP/IP uses special programs in place of the ICF-based communications programs; however, the same user interface is used as for other communications methods. The IBM implementation requires that intermediate files be used to store the EDI data as input or output of the FTP function; these files may be re-used as temporary work files. The characteristics (record length, etc.) of these intermediate files, as well as their locations and names, may be user-controlled through the Network Port definition. Separate intermediate files may be used for different functions.

The special processing is triggered simply by specifying a Network name beginning with the characters “*FTP”. The user may create as many *FTP network definitions as desired. Under such a network, the network port definitions use the same setup panel as those specified under the previously implemented network *FILE. The library, file, and member names in the network port refer to the intermediate file described above.

Since the details of conducting a conversation with an FTP server will in general vary considerably from one server type to another, most of the customization details are specified in the Control Script. There are some new Control Script functions which are used to build FTP scripts, and substantial enhancements to the existing WRTLINE and CMDEXC functions provide the capability to create scripts for any FTP server.

The control script lines containing FTP commands may be created with a large variety of run-time substitution variables, allowing (for example) unique file names to be created using the system date and/or time in many formats. Substitution variables are also available for all Network Port parameters, allowing the same script to be used with any number of Network Ports.