1 ' A short, receive-only Kermit program, suitable for bootstrapping a
2 ' real Kermit program. Assumes no parity, refuses to do 8th bit
3 ' prefixing or repeat-count compression, and depends upon remote
4 ' system to take care of timeouts. Can receive multiple
5 ' files; can receive binary files(?). Written in Microsoft Basic,
6 ' tested on the IBM PC and the DEC Rainbow.
7 '
8 ' F. da Cruz, November 1985
9 '
100 RESET : RESET : RESET ' Seems to help sometimes...
110 ON ERROR GOTO 9000
120 DEFINT A-Z ' Use all integers for speed.
131 '
141 ' All lines with numbers not ending in 0 can be removed.
151 '
161 ' X = 1 ' For diagnostic output
171 ' XX = 1 ' For super-verbose diagnostics
181 '
191 IF XX = 1 THEN X = 1
1000 '
1001 ' Initialize N and PREV (current and previous packet number),
1002 ' the Send packet buffer (with a NAK for packet 0),
1003 ' and open the communication port 1200-baud no-parity no-modem.
1004 ' See your Basic manual for details about OPEN COM options.
1005 '
1010 N = 0 : PREV = -1 : SNDBUF$ = CHR$(1)+"# N3"+CHR$(13)
1020 OPEN "COM1:1200,N,8,,CS,DS" AS #1
1999 '
2000 ' Get remote's Send-Initate parameters then ACK with our own,
2001 ' namely 40-character packets, 10-sec timeout, no padding,
2002 ' CR packet terminator, "#" Ctrl-prefix, no 8th-bit quoting,
2003 ' and single-character checksum. Ignore remote parameters
2004 ' except for packet terminator (EOL$) and Ctrl-prefix (CTL$).
2005 '
2010 PRINT "Waiting..."
2020 GOSUB 5000 ' Wait for a valid packet.
2030 IF TYPE$ <> "S" THEN GOTO 8000 ' Wrong type, fail.
2040 IF LEN(PKTDAT$) > 4 THEN EOL=ASC(MID$(PKTDAT$,5,1))-32 ELSE EOL=13
2050 IF LEN(PKTDAT$) > 5 THEN CTL=ASC(MID$(PKTDAT$,6,1)) ELSE CTL=ASC("#")
2061 IF X THEN PRINT " Send-Init OK, EOL=";EOL;", CTL=";CTL
2070 TYPE$ = "Y" : L = 8 : D$ = "H* @-#N1"
2080 GOSUB 6000 ' Send ACK with own parameters.
2999 '
3000 ' Get a File Header packet. If a B packet comes, we're all done.
3010 GOSUB 5000 ' Wait for valid packet.
3020 IF TYPE$ = "B" THEN GOSUB 7500 : GOTO 9900 ' Done.
3030 IF TYPE$ <> "F" THEN D$ = TYPE$+" Packet in [FB] State" : GOTO 8000
3040 PRINT "Receiving "; MID$(PKTDAT$,1,L) ' Print Message
3050 OPEN MID$(PKTDAT$,1,L) FOR OUTPUT AS #2 ' Open the file (errors fatal)
3060 GOSUB 7500 ' Open OK, Ack the F packet
3999 '
4000 ' Get Data packets. If a Z packet comes, the file is complete.
4010 GOSUB 5000 ' Get a valid packet.
4020 IF TYPE$ = "Z" THEN CLOSE #2 : GOSUB 7500 : PRINT "(OK)" : GOTO 3000
4030 IF TYPE$ <> "D" THEN D$ = TYPE$+" Packet in [DZ] State" : GOTO 8000
4040 PRINT #2, MID$(PKTDAT$,1,P); ' Good data, record in file.
4060 GOSUB 7500 ' Ack the data.
4070 GOTO 4000 ' Go back for more.
4999 '
5000 ' Get a valid packet with the desired sequence number.
5010 GOSUB 7000 ' Read and decode a packet.
5020 FOR TRY = 1 TO 5 ' Try 5 times, then give up.
5030 IF N <> PREV AND TYPE$ <> "Q" THEN RETURN ' Good!
5040 PRINT #1, SNDBUF$; ' Not good, so resend previous,
5050 PRINT "%"; ' and display special blip.
5060 GOSUB 7000 ' Read another packet.
5070 NEXT TRY
5080 TYPE$ = "E" : D$ = "Timed Out" : RETURN ' Failed after 5 tries.
5999 '
6000 ' Send a packet with data D$ of length L, type T$, sequence #N.
6010 SNDBUF$ = CHR$(1)+CHR$(L+35)+CHR$(N+32)+TYPE$+D$+" "+CHR$(EOL)
6020 CHKSUM = 0
6030 FOR I = 2 TO L+4 ' Compute the checksum
6040 CHKSUM = CHKSUM + ASC(MID$(SNDBUF$,I,1))
6050 NEXT I
6060 CHKSUM = (CHKSUM + ((CHKSUM AND 192) \ 64)) AND 63
6070 MID$(SNDBUF$,L+5) = CHR$(CHKSUM + 32) ' Insert the checksum
6080 PRINT #1, SNDBUF$; ' Send the packet
6091 IF X THEN PRINT ">>";MID$(SNDBUF$,1,L+5);"<<"
6100 RETURN
6999 '
7000 ' Routine to Read and Decode a Packet.
7010 FOR TRY = 1 TO 3 ' Try 3 times...
7020 LINE INPUT #1, RCVBUF$ ' Read a "line" (up to a CR)
7030 I = INSTR(RCVBUF$,CHR$(1)) ' Look for the SOH (^A)
7041 IF X THEN PRINT "<<";RCVBUF$;">>, SOH at"; I; ", Try #"; TRY
7050 IF I > 0 THEN GOTO 7100 ' Got SOH, must be a real packet.
7060 NEXT TRY ' No SOH, try again.
7070 TYPE$ = "Q" : D$ = "Timed Out" : RETURN ' No real packet
7100 CHK = ASC(MID$(RCVBUF$,I+1,1)) : L = CHK - 35 ' Length
7110 T = ASC(MID$(RCVBUF$,I+2,1)) : N = T - 32 : CHK = CHK + T ' Number
7120 TYPE$ = MID$(RCVBUF$,I+3,1) : CHK = CHK + ASC(TYPE$) ' Type
7130 P = 0 : FLAG = 0 : PKTDAT$ = STRING$(100,32) ' Data
7141 IF X THEN PRINT " L =";L;"N =";N"T = '";TYPE$;"'"
7200 FOR J = I+4 TO I+3+L ' For all data characters...
7210 T = ASC(MID$(RCVBUF$,J,1)) ' Get a data character
7220 CHK = CHK + T ' Add it to the checksum
7231 IF XX THEN PRINT "-";(MID$(RCVBUF$,J,1));
7240 IF TYPE$ = "S" THEN 7300 ' Don't decode the S packet!
7250 IF FLAG = 0 AND T = CTL THEN FLAG = 1 : GOTO 7400
7260 T7 = T AND 127 ' Use only 7 bits for Ctrl range check
7270 IF FLAG THEN FLAG = 0 : IF T7 > 62 AND T7 < 96 THEN T = T XOR 64
7300 P = P + 1 ' Real data character position
7310 MID$(PKTDAT$,P,1) = CHR$(T) ' Insert data character in buffer
7400 NEXT J
7411 IF XX THEN PRINT " packet data://";MID$(PKTDAT$,1,P);"//"
7420 CHK = (CHK + ((CHK AND 192) \ 64)) AND 63
7430 T = ASC(MID$(RCVBUF$,J,1)) : CHKSUM = T - 32
7441 IF X THEN PRINT " chksum=";CHK;", packet=";CHKSUM;"'";CHR$(T);"'"
7450 IF CHKSUM <> CHK THEN TYPE$ = "Q" ' Compare the checksums.
7460 RETURN ' Return with packet type.
7499 '
7500 ' Routine to send an ACK and increment the packet number...
7510 D$ = "" ' Nothing in Data field.
7520 TYPE$ = "Y" : L = LEN(D$) : GOSUB 6000 ' Send the packet.
7530 PREV = N : N = (N + 1) AND 63 ' Next sequence number, mod 64.
7540 IF N = 0 THEN PRINT "!"; ELSE IF (N AND 4)=0 THEN PRINT "."; ' Blips.
7550 RETURN
7999 '
8000 ' Error packet sender...
8010 IF D$ = "" THEN D$ = "Error"
8020 L = LEN(D$) : TYPE$ = "E" : GOTO 6000 ' Go send it, return from there.
8999 '
9000 ' Error handler, nothing fancy...
9010 D$ = "Error Number" + STR$(ERR) + " at Line" + STR$(ERL)
9020 PRINT CHR$(7);D$
9030 GOSUB 8000 ' Send error packet, and fall through to...
9900 '
9910 ' Normal exit point
9920 CLOSE #1, #2
9930 PRINT CHR$(7);"(Done)"
9999 END