REQ.BAS - A demo requester program

100 ! REQ.BAS - simple program to request CD/ROM server data
110 ! first cut - very simplistic. Needs following things for production:
120 ! 1. OPENING TRM1: needs to have error trapping routine trap device is busy 
130 !  condition, wait a second or so, and try again.
140 ! 2. retry if server request fails. If the comm to the server gets bungled,
150 !  or the server drops a byte receiving a request, or AUTLOG drops a byte
160 !  coming back from server, the job needs to detect the lack of the
170 !  returned data file (INFILE), or a message that tells the request to
180 !  re-submit, and resend the request. Up to five or ten retries should give
190 !  good reliability.
200 !
210 MAP1 OVERLAYS
220 map2 TEXT'AREA,X,150
230 map3 AS'ARRAY(150),b,1,@TEXT'AREA
240 map3 PACKET,s,150,@TEXT'AREA
250 MAP1 STX,s,1,chr(2)
260 MAP1 ETX,s,1,chr(3)
270 MAP1 ID,S,3
280 MAP1 INFILE,s,40
290 MAP1 BUFF,s,512
300 
310 XCALL JOBNO,ID      ! ID gets jobtbl slot number as 3 ascii digits (tag field)
320 INFILE = "CAT"+ID+".DAT"
330 
340 LOOP:
350 KILL INFILE
360 INPUT LINE "Enter REQUEST type 1-5  ", TYPE
370 CALL BUILD'REQUEST
380 TRIES = 0
390 AGAIN:
400 TRIES = TRIES + 1
410 IF TRIES > 10 GOTO SERVER'DEAD
420 ! note that TRM1 is defined with DEVTBL as NON-SHAREABLE
430 ! PCV0001 is the hard coded name of the TRMDEF the server is attached to.
440 OPEN #1,"TRM1:PCSERV",OUTPUT
450 PRINT #1,PACKET;
460 CLOSE #1
470 ! wit for reply - AUTLOG job will WAKE our job when response is done
480 XCALL SLEEP,60
490 LOOKUP INFILE, SIZE
500 IF SIZE = 0 GOTO AGAIN
510 OPEN #2, INFILE, INPUT
520 INPUT LINE #2,BUFF
530 ? BUFF
540 CLOSE #2
550 GOTO LOOP
560 
570 SERVER'DEAD:
580 PRINT "The catalog server is offline."
590 END
600 
610 ! This routine builds the server request packet
620 BUILD'REQUEST:
630 PACKET = SPACE(150)
640 PACKET[1,1] = STX
650 PACKET[2,4] = TYPE USING "#ZZ"
660 PACKET[5,7] = ID     ! this is the tag field
670 PACKET[8,15] = 150 USING "#ZZZZZZZ"
680 IF TYPE = 3 PACKET[16,17]="52"     !makes for '52
690 IF TYPE = 4 PACKET[16,20]="52NAS"     !models for '52 NASH
700 IF TYPE = 5 PACKET[16,23]="52NASCOU"     !models for '52 NASH COUPE
710 PACKET[150,150] = ETX
720 CALL CALC'CHECKSUM
730 RETURN
740 
750 ! Calculate checksum as ls 8 bits of of sum of all bytes in packet
760 CALC'CHECKSUM:
770 CSUM = 0
780 FOR I= 1 to 146
790 CSUM = CSUM + AS'ARRAY(I)
800 NEXT I
810 CSUM = (CSUM AND 255)
820 PACKET[147,149] = CSUM USING "#ZZ"
830 RETURN
840 
850 ! end of REQ.BAS