Siemens CP 1242-7 GPRS V2 Operating Instructions Manual page 17

Direct communication between stations
Figure 2-3
In this configuration, two SIMATIC S7-1200 stations communicate directly with each other
using the CP 1242-7 GPRS V2 via the GSM network. Each CP 1242-7 GPRS V2 has a fixed
IP address. The relevant service of the GSM network provider must allow this.
TeleService via GPRS
In TeleService via GPRS, an engineering station on which STEP 7 is installed communicates
via the GSM network and the Internet with the CP 1242-7 GPRS V2 in the S7-1200.
Since a firewall is normally closed for connection requests from the outside, a switching
station between the remote station and the engineering station is required. This switching
station can be a telecontrol server or, if there is no telecontrol server in the configuration, a
TeleService gateway.
CP 1242-7 V2
Operating Instructions, 05/2014, C79000-G8976-C311-00
Direct communication between two S7-1200 stations
Configuration examples
1.5 Requirements for operation
17