Tunnel – Advanced 4G-RS232 Tunnel – Setting up the MTX Tunnel as a permanently connected TCP/IP Server and configured to send the IP address to a web server by HTTP

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Scenario details:

  • We need to monitor 100 devices with an RS232 port (115200.8.N.1 and HW flow control) from a central control station using a GPRS link. This will be done using the MTX-Tunnel acting as a transparent serial – 4G tunnel
  • Access to the RS232 remote devices at any time is mandatory, so the modem connected to the serial port device (which needs to be controlled) must remain permanently connected to 4G waiting for a connection. Access to the modems must only be allowed for the IP coming from the PC Control (200.200.200.200) and also for a backup IP coming from the central office fiber line, whose IP is: 200.200.200.201
  • In order to reduce costs, SIM cards will use dynamic IP addressing. As we have a large number of modems, we will not use DynDNS. So MTX Tunnel will send the IP every time that it the WEB server has been assigned a new one by HTTP (the IP address value assigned by the GSM operator). Every time a modem changes the IP address, the modem must send the new IP address value to the control centre (with URL http://www.miweb.com/datosIP.asp and port 8080). This way the external WebServer will store the IP in a SQL server database so the PC control centre has access to the devices at all times

Solution: MTX-Tunnel firmware + MTX-Java-IoT/MTX-Java-T/MTX-Java-T2

Config.txt configuration file:

Configuration Observations
COMM_baudrate: 115200
COMM_bitsperchar: 8
COMM_autocts: on
COMM_autorts: on
COMM_stopbits: 1
COMM_parity: none
GPRS_apn: movistar.es
GPRS_login: MOVISTAR
GPRS_password: MOVISTAR
GPRS_DNS: 8.8.8.8
GPRS_timeout: 0
MTX_PIN: 0000
MTX_model: MTX-4G-JAVA-IOT-STD-N
MTX_mode: server
MTX_urc: off
TCP_port: 20010
FIREWALL_enabled: on
FIREWALL_IP1: 200.200.200.200
FIREWALL_IP2: 200.200.200.201
DNS_enabled: on
DNS_mode: http
DNS_httpMode: get
DNS_password: 12345678
DNS_server: miweb.com:8080/datosIP.asp
DNS_extended: off		 Serial port baud rate
8 bit data
CTS hardware control enabled
RTS hardware control enabled
1 stop bit
No parity
GPRS APN from your network operator
GPRS Login
GPRS Password
Google DNS. Must be used if TCP_IP is set to DNS
Value 0 means MTX-Tunnel is always connected
If SIM card has no PIN security, use 0000
MTX terminal modem model used
TCP server mode
URC messages will not be sent
TCP port used
Enabled to accept authorized IPs
This IP can only connect to remote modem
This IP can only connect to remote modem
DNS service enabled
GPRS IP address sent using HTTP GET
It will be reported by HTTP GET
Password string sent in DNS communication
DNS server URL
GPIO and ADC values extra information is not sent

Details:

  • Bear in mind that when using HTTP, if you use a TCP port different to the standard HTTP (TCP 80), the port must be included in the parameter “DNS_server” and not in “DNS_port”
  • Each time MTX-Tunnel changes the IP address, it will connect through and use the following URL: http://www.miweb.com:8080/datosIP.asp?IMEI=&PASS=12345678&IP=
  • The web server will receive the parameters sent by the MTX-Tunnel and store the IP address in a database. You can collect the parameters from the ASP page by inserting this example code in “datosIP.asp”.
<%
IMEI=Request.QueryString (“IMEI”)
Password=Request.QueryString (“PASS”)
IP=Request.QueryString (“IP”)
%>
  • If you prefer (recomended), you can send data to the server in JSON format via GET or POST. For example, if you wanted to send data in JSON format via HTTP GET, you would have to modify  the configuration with something like this:
Configuration Observations
DNS_server: www.miweb.com:8080/datosIP.asp?data=
DNS_httpMode: getjson		 URL where the IP will be sent
Data will be sent in JSON format
  • And to send data in JSON format via HTTP POST you would have to modify the configuration the following way:
Configuration Observations
DNS_server: www.miweb.com:8080/datosIP.asp
DNS_httpMode: postjson		 URL where the IP will be send
Data will be sent in JSON format
  • When your modem is configured in getjson / postjson mode it will send a JSON with the following format:
{“IMEI”:357042060366409,”TYPE”:”DNS”,”P”:”12345678”,”IP”:”88.28.253.206”, “CSQ”:26,”VER”:”9.12”,”AUX”:””,”MOD”:”201”}

Where each parameter is: 

IMEI the unique identification number of the modem
TYPE type of JSON sent (DNS in this case)
P user’s field specified in DNS_password parameter
IP modem’s current IP
CSQ rssi of the modem (between 0 and 31)
VER MTX-Tunnel version
MOD MTX modem model