I m trying to access a website using sim900 GSM module. This is the list of commands
AT+CSQ
+CSQ: 16,0
OK
AT+HTTPINIT
OK
AT+
I have encoutered this error as well. The cause of the problem may be that there is not enough money in the phone number account. You may check it.
I have found that when an http call is made to an https only website it will throw a 601 error on the sim. Beware some sim devices have ssl and some don't. Use AT+HTTPSSL=? to interrogate. device with ssl will respond like, 'HTTPSSL 1'. If you get an error your device doesn't have ssl. This took some work with the factory for me to determine this.
You must also use to hit ssl site. I am using the wifi101 ssl client.
fona.setHTTPSRedirect(true); dy3