ESP8266 WiFi Module with multi-session HTTP API (pure MMBasic)

'
'ESP8266 Module. Andrew Henderson. October 2016
'

'Preamble
	OPTION BASE 0

	CONST LAN=2


'S/W Init
	DIM STRING A$,B$,D$
	DIM STRING LNBuf$
	DIM STRING LANRxLN$,LANTxLN$,TChr$ LENGTH 1
	DIM INTEGER C,Z,TOFg,Chan,Conn(4),PingTMR,PingCtr,RL1TMR LANf
	DIM FLOAT x

	'Starting WLAN Interface

	Open "COM2:9600,1024" As #LAN

	ESP8266Reset


Main:



        ' don't do this every time through the loop, set a timer for no more than 60second intervals {
        'Test Internet connectivity - you'll have to handle what to do if this is broken, there's nothing here for it.
	A$=ESP8266Exec$("AT+PING="+PA,4000,0)   ' PA=Ping address. try to be nice here and set this to a DNS server from your ISP e.g. 100,200,111,222 or www.bbc.co.uk or something that won't mind you pinging them
	IF A$="OK" THEN
		'good
		'...
	ELSE
		'internet down
                '...
	END IF
        }





	'Web API parsing

	LANRxLN$=GetIO$(LAN,1)
	IF LANRxLN$="" OR LANRxLN$="T/O" THEN GOTO Main ' nothing waiting on the input

	IF MID$(LANRxLN$,2,8)=",CONNECT" THEN ' ESP8266 provides the connect as an indication of HTTP input
		Chan=VAL(LANRxLN$)
		IF Chan>=0 AND Chan<=4 THEN
			Conn(Chan)=1 
                        PRINT "Inbound connect channel "+STR$(Chan)
			'Inbound connect channel on  channel 0 - 5
			GOTO IPEXIT
		END IF
	END IF

	IF MID$(LANRxLN$,2,7)=",CLOSED" THEN ' ESP8266 provides the closed as an indication of HTTP channel closing
                                             ' either coz it was explicit or it timed out
		Chan=VAL(LANRxLN$)
		IF Chan>=0 AND Chan<=4 THEN
			IF Conn(Chan)=0 THEN A$=" Abnormally " ELSE A$=""
			PRINT "Closed channel "+STR$(Chan) + A$
			Conn(Chan)=0
			GOTO IPEXIT
		END IF
	END IF

	IF LEFT$(LANRxLN$,5)="+IPD," THEN
		Chan=VAL(MID$(LANRxLN$,6,1))
		IF Chan>4 THEN GOTO IPDerrEXIT
		IF Conn(Chan)<>1 THEN GOTO IPDerrEXIT 'channel not open

		z=INSTR(LANRxLN$,":GET /<my page, e.g. index.htm>") ' +IPD,0,nnn:GET /index.htm HTTP/1.1

		do:a$=GetIO$(LAN,2):loop until a$="Connection: Keep-Alive" ' empty the rest of the envelope, this string is the last part of an HTTP connection header

		IF z=>8 AND Z<=11 THEN ' checking for the position of the arguments in the string - your mileage will vary... simple sanity check
			b$=MID$(LANRxLN$,z+13)
			z=INSTR(b$," HTTP/")
			IF z<21 THEN GOTO IPDerrEXIT '... and again
			b$=LEFT$(b$,z-1) ' remove the HTTP bit
			b$=Replace$(b$,"+"," ")' + to spaces
			args=Split(b$,"?") '  split the request arguments out
			IF args <3 THEN GOTO IPDerrEXIT ' your arguments might vary - I have two, the header + two arguments = 3 strings from the spilt
			
			FOR n=2 TO args 'args=1 is a dummy
				SELECT CASE LEFT$(ucase$(SP$(n)),4) ' check for the name of the argument here and assign the value to a variable
					CASE "VAR1="
						var1$=LTrim$(RTrim$(MID$(sp$(n),5)))
					CASE "VAR2="
						var2$=LTrim$(RTrim$(MID$(sp$(n),5)))
				END SELECT
			NEXT
			IF var1$="" OR var2$="" THEN GOTO IPDerrEXIT ' don't allow empty values - your mileage may vary
			ERASE SP$
			Msg$=URLDecode$(Msg$)

                ' other api calls go here, I only have one in this application


		END IF

		GOTO IPDerrEXIT 'default action IF we don't find an API call

	END IF


	GOTO IPEXIT
IPDerrEXIT:
	B$="ERROR: Malformed request {"+LANRxLN$+"}"
IPOKEXIT:

	PRINT #LAN,"AT+CIPSENDEX="+STR$(Chan)+",255" ' send our response back to the requestor
	PAUSE 100

	PRINT#LAN,B$+"\0"
	PAUSE 100

	PRINT#LAN,"AT+CIPCLOSE="+STR$(Chan) ' then close the channel nicely
	Conn(Chan)=0

IPEXIT:

	GOTO Main

	END


'------------------ ESP8266 WiFi Modem SUBsys -------------

	SUB ESP8266Reset
		LOCAL STRING A$
		LOCAL INTEGER N

		PULSE LANRST,10                                ' whatever pin you have connected to the reset of the ESP8266
		PAUSE 400

		LANExec "ATE0",2,0
		LANExec "AT+CWAUTOCONN=0",2,0                  ' turn off autoconnect while we initialise
		LANExec "AT+CWMODE=1",2,0
		LANExec "AT+CWQAP",4,0                         ' disconnect any existing WiFi connections
		LANExec "AT+RFVDD",2,0
		LANExec "AT+CWJAP="+AP+","+PW,10,1             ' AP= name of the network you want to join e.g. your WIFI SSID - and PW= it's password
		LANExec "AT+CIPSTA="+IP+","+GW+","+MS,2,0      ' the IP and Gateway address for static IP addresses, rem this line for a static IP
		LANExec "AT+CIFSR",2,0
		LANExec "AT+CWAUTOCONN=1",2,0                  ' turn autoconnect back on so if the WiFi drops, the ESP8266 will self negotiate to get it back
		LANExec "AT+CIPMUX=1",2,0
		LANExec "AT+CIPSERVER=1,19090",2,0             ' turn on the server with the port you want your API to listen on, normally HTTP is 80 or sometimes 8080, here I listen on 19090... you can use anything from 1 - 65536 but as a guideline; avoid anything below 1000 if you are not using 80

		LANTxLN$="":LANRxLN$=""                        ' buffers for receive and transmit

		FOR N=0 TO 4:Conn(N)=0:NEXT                    ' clear the channel connection flags

	END SUB




	SUB LANExec(CM$,T,Suppress) 'temp - will go when we have better handling of the startup
		LOCAL STRING A$
		A$=ESP8266Exec$(CM$,T,Suppress)
		IF Suppress<2 THEN CLog A$,0
	END SUB

	FUNCTION ESP8266Exec$(Com$,TimeOut,Obf)
		LOCAL STRING A$ LENGTH 1,LN$
		LOCAL INTEGER C

		PRINT #LAN,Com$

		DO
			LN$=GetIO$(LAN,TimeOut)
			IF LN$="T/O" THEN ESP8266Exec$="T/O":EXIT DO
			IF LN$<>"" THEN
				IF Obf<2 THEN CLog "["+LN$+"]",0
				IF LN$="OK" OR LN$=">" OR LN$="SEND OK" THEN ESP8266Exec$=LN$:EXIT DO
				IF INSTR(LN$,"ERROR") THEN ESP8266Exec$="ERROR ["+LNBuf$+"]":EXIT DO
			END IF
		LOOP

	END FUNCTION


'----------------------------------------------------


	FUNCTION GetIO$(io,TimeOut)
		LOCAL STRING a$,b$
		LOCAL INTEGER c

		StartTOTimer TimeOut
		DO
			IF TOFg=1 THEN GetIO$="T/O":EXIT DO
			IF LOC(#io)<>0 THEN
				A$=INPUT$(1,#io):C=ASC(A$)
				SELECT CASE C
					CASE 13
						GetIO$=b$:EXIT DO
					CASE 0 TO 31
					CASE ELSE
						IF LEN(b$)+LEN(a$)<255 THEN b$=b$+a$ ELSE b$=a$
				END SELECT
			END IF
		LOOP
		ClearTOTimer
	END FUNCTION


	SUB FlushIO(stream)
		LOCAL STRING A$
		DO WHILE LOC(#stream)<>0
			PAUSE 50:A$=INPUT$(LOC(#stream),#stream):PAUSE 50
		LOOP
	END SUB



	FUNCTION Replace$(a$,b$,c$)
		LOCAL INTEGER z
		LOCAL STRING x$,y$
		z=1
		DO
			z=INSTR(z,a$,b$)
			IF z=0 THEN EXIT DO
			x$=LEFT$(a$,z-1):y$=MID$(a$,z+LEN(b$)):a$=x$+c$+y$:z=LEN(x$)+LEN(c$)
		LOOP
		Replace$=a$
	END FUNCTION


	FUNCTION URLDecode$(a$)
		LOCAL INTEGER z
		LOCAL STRING b$,c$
		z=1
		DO
			z=INSTR(z,a$,"%")
			IF z=0 OR z=LEN(a$) THEN EXIT DO
			b$=MID$(a$,z,3):c$=CHR$(VAL("&h"+MID$(b$,2))):a$=Replace$(a$,b$,c$)
		LOOP
		URLDecode$=a$
	END FUNCTION


	FUNCTION LTrim$(a$)
		LOCAL INTEGER m
		FOR m=1 TO LEN(a$)
			IF not(MID$(a$,m,1)=" " OR MID$(a$,m,1)=CHR$(9)) THEN LTrim$=MID$(a$,m):EXIT FUNCTION
		NEXT
		LTrim$=""
	END FUNCTION


	FUNCTION RTrim$(a$)
		LOCAL INTEGER n
		FOR n=LEN(a$) TO 1 STEP -1
			IF not(MID$(a$,n,1)=" " OR MID$(a$,n,1)=CHR$(9)) THEN RTrim$=LEFT$(a$,n):EXIT FUNCTION
		NEXT
		RTrim$=""
	END FUNCTION


	FUNCTION Split(a$,b$)
		LOCAL INTEGER z,n,m
		ON ERROR SKIP
		ERASE SP$
		z=1:n=0
		DO
			z=INSTR(z,a$,b$)
			IF z=0 THEN
				IF n=0 THEN
					DIM SP$(1):SP$(1)=a$:Split=1:EXIT FUNCTION
				ELSE
					EXIT DO
				END IF
			ELSE
				n=n+1:z=z+LEN(b$)
			END IF
		LOOP

		m=n+1:n=1
		DIM SP$(m)
		DO
			z=INSTR(1,a$,b$)
			IF z=0 THEN
				SP$(m)=a$:EXIT DO
			ELSE
				SP$(n)=LEFT$(a$,z-1):a$=MID$(a$,z+LEN(b$)):n=n+1
			END IF
		LOOP
		Split=m
	END FUNCTION