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+With all the network cards for the C64 these days, a user-friendly IP address input/parsing routine might be handy.   Here's one I wrote for Artillery Duel - could be optimized, but hopefully easy to follow.
+Use in conjunction with the [[robust_string_input]] code.  DASM.
+<code>
+; ======================================
+; IP Address Input routine - Schema/AIC
+; ======================================
+;Converts e.g.
+;192.168.1.64
+;to
+;ABC ABC ABC ABC
+;192.168.001.064
+;and then to 4 bytes at gotip
+include "robust_string_input.asm"
+IPADDRESS_FILTER
+  dc.b "1234567890.",0
+getip
+  lda #$00
+  sta $cc        ; Force cursor to flash
+  lda #>IPADDRESS_FILTER
+  ldx #<IPADDRESS_FILTER
+  ldy #15
+  jsr FILTERED_INPUT
+  jsr CONVERTIP
+  lda #$01
+  sta $cc        ; Force cursor to not flash
+  lda #$20
+  jsr $ffd2      ;overwrite cursor detritus
+  rts
+gotip
+ dc.b $00,$00,$00,$00
+;===========================
+DOTS
+  dc.b #$00
+STRINDEX
+  dc.b #$00
+IPINDEX
+  dc.b $00
+CONVERTIP
+  ;First, check that there are three periods '.' in the string.
+  ldx #$00
+  sta DOTS
+  sta IPINDEX
+  sta STRINDEX
+COUNTLOOP
+  lda GOTINPUT,x
+  beq DONECOUNT   ; end of string (0)
+  cmp #'.
+  bne COUNTNEXT
+  inc DOTS
+COUNTNEXT
+  inx
+  jmp COUNTLOOP
+DONECOUNT
+  lda DOTS
+  cmp #$03
+  beq DOTSOK
+  jmp INVALIDIP
+; OK, now pad the values if needed for the conversion, one octet at a time
+DOTSOK
+;Init A,B,C with 0
+NEXTBYTE
+  lda #$0
+  sta A
+  sta B
+  sta C
+BYTELOOP
+  ldx STRINDEX
+  lda GOTINPUT,x
+  beq ENDOFBYTE   ;end of string (0)
+  cmp #'.
+  beq ENDOFBYTE
+  ;Shift ABC over
+  ldy B
+  sty A  ;old A is lost
+  ldy C
+  sty B
+  sbc #$30  ;Convert from PETSCII to equivalent value
+  sta C     ;insert new digit
+NEXTDIGIT
+  inc STRINDEX
+  jmp BYTELOOP
+ENDOFBYTE
+  jsr dec2hex   ;Returns byte in accumulator, carry set if >255
+  bcs INVALIDIP
+  ;Save the returned byte
+  ldy IPINDEX
+  sta gotip,y
+  inc IPINDEX
+  lda IPINDEX
+  cmp #$04      ;Done
+  beq IP_DONE
+  inc STRINDEX  ;Skip over the '.'
+  jmp NEXTBYTE
+IP_DONE
+  rts
+INVALIDIP
+  ; ERROR MESSAGE HERE!
+  inc $d020
+  jmp INVALIDIP
+  rts
+;===================================================
+; Convert three-digit decimal (ABC) into a byte
+;===================================================
+dec2hex
+  lda A
+  jsr MULT10
+  jsr MULT10   ;x100
+  sta TMP0
+  lda B
+  jsr MULT10   ;x10
+  sta TMP1
+  lda C
+  sta TMP2     ;x1
+  clc
+  lda #$00
+  adc TMP0
+  adc TMP1
+  adc TMP2
+  rts     ;Carry will be set if result was > 255
+; ===================
+TMP0
+ dc.b #$00
+TMP1
+ dc.b #$00
+TMP2
+ dc.b #$00
+A                 ;First digit
+ dc.b #$00
+B                 ;Second digit
+ dc.b #$00
+C                 ;Third digit
+ dc.b #$00
+; =======================================================================
+; Multiply by 10 - from http://www.6502.org/source/integers/fastx10.htm
+MULT10  ASL         ;multiply by 2
+        STA TEMP10  ;temp store in TEMP
+        ASL         ;again multiply by 2 (*4)
+        ASL         ;again multiply by 2 (*8)
+        CLC
+        ADC TEMP10  ;as result, A = x*8 + x*2
+        RTS
+TEMP10   .byte 0
+</code>