+HTTPACTION: 0,601,0 on SIM800L error getting webpage

Question

I can't take a HTML page with SIM800L GSM modem.

I open connection

AT+CSCS="GSM"
AT+CMGF=1
AT+SAPBR=3,1,"APN","apn.fastweb.it"
AT+SAPBR=1,1
AT+SAPBR=2,1
+SAPBR: 1,1,"10.44.96.11"

I define HTTP param:

AT+HTTPINIT
AT+HTTPSSL=1
AT+HTTPPARA="CID",1
AT+HTTPPARA="REDIR",1
AT+HTTPPARA="URL","https://www.gevaelettronica.it/"
AT+HTTPACTION=0
+HTTPACTION: 0,606,0

SSL is working

AT+HTTPSSL?
+HTTPSSL: 1

IP there are:

AT+SAPBR=2,1
+SAPBR: 1,1,"10.44.96.11"
AT+CIFSR
ERROR

if error, need to check PDP parameter. What is PDP ?

AT+CGDCONT?
+CGDCONT: 1,"IP","","0.0.0.0",0,0
+CGDCONT: 2,"IP","","0.0.0.0",0,0
+CGDCONT: 3,"IP","","0.0.0.0",0,0

Nobody uses this command +CGDCONT

AT+CGDCONT=1,"IP","apn.fastweb.it"
AT+CGDCONT?
+CGDCONT: 1,"IP","apn.fastweb.it","0.0.0.0",0,0
+CGDCONT: 2,"IP","","0.0.0.0",0,0
+CGDCONT: 3,"IP","","0.0.0.0",0,0

AT+CIFSR     ERROR

expected is

+HTTPACTION: 0,200,0

Answer 1

PDP is short for Packet Data Protocol, and is used in mobile network context in relation to packet switched data communication (as opposed to circuit switched communication). The first evolution of support for this was called GPRS in late 90's/early 2000's. Later technological successors were UMTS and LTE.

For more details there is a whole chapter 10 Commands for Packet Domain in the 3GPP 27.007 specification which is rather technical - after all the specification is indented as a specification with all required details for companies to implement phones/networks supporting the technology, although it also describes the behaviour and parameters of the packed switched commands like AT+CGDCONT etc, so it is kind of important and useful information as well.

So by all means read it, but do not set your expectation that you to be able to read the whole chapter and fully understand all the details. I think the best approach is to start reading the description for each of the commands you are using, and then "expand outwards" as needed (that's how professionals read those specifications. Nobody starts on page one and reads all the way till the end (unless your assignment is and you are paid to proofread I guess)).

I was not highly involved in packet switched data communications, so I do now know/remember much more details than I have written above. If on the other hand you have questions about mobile circuit switched data calls, boy can I give you more detailed answers!