TN3270 Server Manual

CRT Communication Protocol

TN3270 Server Manual—424097-001

5-8

SNAX/XF Mode

You can configure the Guardian TN3270 Server process to emulate the SNAX/XF

application interface by specifying the -s switch on the command line. The Guardian

TN3270 Server runs in AM3270 mode by default.

The following file system procedures are recognized by the TN32SERV/CRT protocol

when it is operating in SNAX/XF mode:

Two-Step READ Requests

The TN3270 CRT protocol for SNAX provides a two-step READ capability that helps

your application processes make the most efficient use of the available buffer space. A

two-step READ involves two separate READ operations.

•

The first READ operation, initialized by a WRITEREAD call (that has a write count

of 0 and a read count of 2), returns an integer to the first word of the buffer,

indicating how many bytes of data are in the incoming data block.

•

The second READ operation, initialized by a READ call, accepts the incoming data

block.

SNAX/XF CRT SETMODE Procedure

Applications use SETMODE calls to control a Guardian TN3270 Server session and to

obtain information about it. The CRT SETMODEs that have special significance to the

Guardian TN3270 Server when it is in SNAF/XF mode are described next.

SETMODE Function 144 Procedure

The SETMODE function 144 procedure is used in a SNAX environment to find the

single-byte character set and double-byte character set (if any) that is defined for the

logical unit (LU). In a Guardian TN3270 Server environment, a SETMODE function

144 procedure returns hard-coded values for the Katakana (single-byte) and Kanji

(double-byte) character set codes. If the -k command line option is not selected, the

single-byte character set code returned is 9 for EBCDIC. The double-byte character set

code is 0, indicating no double-byte character set is used. If the -k option is selected, the

single-byte character set code returned is 14 for Katakana EBCDIC. The double-byte

character set code is 3 for IBM MIXED.

AWAITIO CONTROL OPEN SETMODE WRITEREAD[x]

CANCEL DEVICEINFO READ[x] SETPARAM

CLOSE FILEINFO SETMODE WRITE [x]