GPRS IP MODEM Data in PROT mode

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GPRS IP MODEM Data in PROT mode

   Four-Faith GPRS IP MODEM Data sends three types of data packets to data center in total when working in PORT mode：the registration packet when first regist,the data packet that including application data,the heartbeat packet that maintain links.The format description of three types of packets as follow:
1.The registration packet when first regist:
   Format:
ID      PHONE_NUMBER    0           IP_ADD          ETX
4 bytes     11 bytes         1 byte     4 bytes        1 byte
Description:
   ID:                   8 bits of HEXID number
PHONE_NUMBER:        11 bits of ASCII code of mobile phone number.
IP_ADD:              Dynamic IP address(HEX)
ETX:                 0x00 means the end of the data。

For Example: 78 56 34 12 31 33 30 36 36 36 36 38 38 38 38 00 c0 a8 01 42 00
Analytic as follows:
78 56 34 12 Means ID number is: 0x78563412 (4 byte in total)
31 33 30 36 36 36 36 38 38 38 38 Means mobile phone number is：13066668888
c0 a8 01 42 Means IP address is：192.168.1.66

According to your configuration of data center IP and port, GPRS IP MODEM will connect to data center automatic after power on. Once TCP link establish success, GPRS IP MODEM will send first registration packet that including the basic information of GPRS IP MODEM, then it will send data packet of application and heartbeat packet that maintain link.

2. The data packet that including application data:
In the mode of PROT,It will go on data changing when GPRS IP MODEM send data and receive data form data center,the data changing role as follow:
(1)   When GPRS IP MODEM sending data to data center,it change all of the 0xfd to 0xfd0xed first,and change all of the 0xfe to oxfdoxee.
(2)   When GPRS IP MODEM receiving data from data center,it change all of the 0xfdoxed to oxfd first,and change all of the 0xfd0xee to 0xfe.
(3)   Our dynamic library has done the reverse data changing when receiving data,so the packet is completely transparent when using our dynamic library to send and receive data. You must do the reverse data changing in your program if you don’t using the dynamic library we provided,that means change all of the 0xfd0xed to 0xfd first and change all of the 0xfd0xee to 0xfe when the data center receiving data.And change all of the 0xfd to 0xfd0xed first and change all of the 0xfe to 0xfd0xee when sending data to GPRS IP MODEM.
3. The heartbeat packet:
In order to maintain links, GPRS IP MODEM will send 1 byte hearthbeat packet to data center periodic:0xfe
This byte data has been filtered in the dynamic library that we provide.
   Note：After GPRS IP MODEM login in the data center software.Sending character string “***COMMIT CONFIG***” by using data center software, GPRS IP MODEM will enter remote configuration state. Then we can set the GPRS IP MODEM configuration by sending AT commands remotely.