# SIM900 GPRS doubts **URL:** \ **Category:** Wireless & IoT\ **Created:** [November 16, 2012, 2:35pm UTC](https://community.sparkfun.com/t/sim900-gprs-doubts/25432 "2012-11-16T14:35:31Z")\ **Posts on this page:** 1\ **Page:** 1
**Author:** ![SebaS](https://avatars.discourse-cdn.com/v4/letter/s/ccd318/32.png) [@SebaS](https://community.sparkfun.com/u/SebaS)\ **Post date:** [November 16, 2012, 2:35pm UTC](https://community.sparkfun.com/t/sim900-gprs-doubts/25432/1 "2012-11-16T14:35:31Z")
Hello to all!! I can successfully transfer data with a Server. But I’ve seen a lot of ways to start a connection. Now, my goal is to make the device a little more roboust, to prevent malfunction Right now, the command sequence I use to connect to the server is: 1- AT+CGATT = 1 2- AT+CSTT=“”,“”,“” 3- AT+CIICR 4- AT+CDNSCFG = “8.8.8.8”,“8.8.4.4” (Google DNS) 5- (wait for IP STATUS) 6- AT+CIPSTART=“TCP”,“”,“” I do not make use of any of those AT Commands: AT+CIPCSGP AT+CLPORT AT+CIPMUX AT+CIPMODE AT+CGDCONT AT+CDNSORIP Should I use them? All of them or just a few? I mean, if for example CDNSORIP is changed (for any reason) to IP mode and I’m sending domain name, then I guess I won’t be able to connect. So maybe it would be a good idea to set CDNSORIP to be DNS before starting the connection. Also there are some of them I’m not sure I understand it’s functionallity, and please correct me if I’m wrong: **AT+CIPCSGP** : With this command I should set the connection to be GPRS instead of CSD, and also set the APN. This APN has to be the same in **AT+CSTT** , but why configure the APN two times, isn’t one enough? **AT+CLPORT** : Set the Protocolo and the Port… but why, if I already set them in CIPSTART? **AT+CIPMUX** : For now, single connection, so should be always set to 0 **AT+CIPMODE** : I will always use NORMAL MODE **AT+CGDCONT** : This is the one that confuse me the most. I don’t understand what is it for. And again APN is requiered I hope you can help me and clarify my mind. Thanks in advance!