The order in which you call SNA IMF intrinsics depends on
whether your device or the host system will be the first to send
data after a communication path is opened. If the host has a screen
of data waiting for you, the host will want to send the screen before
allowing you to send any data. If the host system requires you to
log on or start the host application, your device must send the
first screen of data to the host system.
You can simplify your program by developing routines that
consist of commonly used sequences of intrinsics. Be sure these
routines check the value returned in the result parameter of each intrinsic. Appendix F “Sample Programs” contains
complete sample programs.
Following are suggested intrinsic sequences, presented to
help you get started writing your programs. You may want to run
Pass Thru with the format parameter in the info string set to three or four (the automatic
print option), to verify the correct intrinsic calling sequence. See Using
SNA IMF Pass Thru for more information.
Host Transmits Data First |
 |
If you expect the host to send data to your device first,
use intrinsics in a sequence like this:
Establishing communications with the host:
- OPEN3270
Establish communications with the host system.
- RECV3270
Check to see if the data has been received.
- RECV3270
Accept an initial screen of data from the host.
- SCREENATTR
Determine the number of fields in the screen and update
the cursor variables containing the coordinates of the cursor position.
Reading data, from a specified field:
- FIELDATTR
Determine the attribute values for a specified field.
- READFIELD
Read data from a specified field in the screen.
(Repeat the FIELDATTR/READFIELD sequence as many times as necessary.)
Reading data, from part or all of the screen:
- ATTRLIST
Return the locations of the attribute characters.
- READSCREEN
Read data from part or all of the screen.
Writing data, into one field at a time:
- WRITEFIELD
Write data into an unprotected field.
Writing data, into several fields at a time:
- SCREENATTR
Update the cursor (row/column) variables again.
- STREAM3270
Write data into several fields at one time.
- TRAN3270
Send a data screen to the host system.
Receiving another screen of data from the host:
- RECV3270
Accept a new data screen from the host.
- SCREENATTR
Determine the number of fields in the screen and update
the cursor variables containing the coordinates of the cursor position.
- FIELDATTR
Determine the attributes of the fields specified.
Closing a session with the host:
- CLOSE3270
Disassociate your terminal from an SSCP-LU session.
Terminal Transmits Data First |
|
If you expect to send data to the host system first, use the
intrinsics in a sequence like this:
Sending data to the host first:
- OPEN3270
Establish communications with the host.
- RECV3270
Accept the SNA IMF banner message.
- TRAN3270
Send the [SYS REQ] key, which puts you into the LU-SSCP session and allows
you to send data to the host.
- RECV3270
Receive a blank SSCP-LU screen.
- WRITEFIELD
Write to the LU-SSCP screen.
- TRAN3270
Send the data screen to the host.
- RECV3270
Accept a new screen of data from the host.
- SCREENATTR
Determine the number of fields in the screen and update
the variables containing the coordinates of the cursor position.
Reading data, from a specified field:
- FIELDATTR
Determine the field attribute values for a specified field.
- READFIELD
Read data from a specified field in the screen.
(Repeat the FIELDATTR/READFIELD sequence as many times as necessary.)
Reading data, from part or all of the screen:
- ATTRLIST
Return the locations of the attribute characters.
- READSCREEN
Read data from part or all of the screen.
Closing a session with the host:
- CLOSE3270
End communications with the host.
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 | NOTE: Be sure to log off from the host application you are
using before you issue the CLOSE3270 intrinsic. The CLOSE3270 intrinsic terminates your session with the host
system, but it does not terminate the host application. If you call CLOSE3270 before you log off from the host application,
the host application is left running, and you have no way of terminating
it, because your session has been closed. |
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| |
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For complete example programs, in non-transparent and transparent mode,
see Appendix F “Sample Programs”
