Tunnel – MTXTunnel configured as TCP/IP server and occasionally connected to LTE/4G. Dynamic IP addressing. Firewall and authorized phone numbers active

Scenario details:

• There are 3 RS232 devices configured as 9600, 8, N, 1 and no flow control. We need to control and monitor from a central server using the 3G-Serial tunnel gateway
• You need to access them occasionally with a remote control, so the modem connected to the remote devices does not need to be permanently connected to the 4G
• The modem will connect to the 4G for 10 minutes, but only after receiving a missed call or an SMS with the text string “on” from any phone number. The modem responds to same phone number with an SMS detailing the IP address obtained from the network
• Then, the modem will connect to the 4G waiting for an input connection request in TCP port number 20010
• We will use a dynamic IP address with network operator SIM cards.
• For more security, modems will only respond to incoming missed calls or special SMSs from authorized phones. Another security feature is that MTX-Tunnel’s modem will only accept an incoming connection from a specific IP address. For example in this case: 200.101.102.103

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

Config.txt configuration file:

Configuration

Observations

COMM_baudrate: 9600 COMM_bitsperchar: 8 COMM_autocts: off COMM_autorts: off COMM_stopbits: 1 COMM_parity: none GPRS_apn: movistar.es GPRS_login: MOVISTAR GPRS_password: MOVISTAR GPRS_timeout: 10 MTX_PIN: 0000 MTX_model: MTX-IOT-4G MTX_mode: server MTX_urc: off TCP_port: 20010 FIREWALL_enabled: on FIREWALL_IP1: 200.101.102.103 SMS_allPhones: off SMS_sendIP: on SMS_validPhone1: +34666123456SMS_dafaultPrefix: +34 SMS_validPhone2: +34666123457 SMS_dafaultPrefix: +34

Serial port baud rate 8 bit data CTS flow control disabled RTS flow control disabled 1 stop bit No parity GPRS APN from your network operator GPRS Login GPRS Password Connected 10 min if there’s no serial data traffic If SIM card doesn’t have PIN security, use 0000 MTX-Terminal modem model used TCP server mode URC messages will be not output TCP port used Enabled to accept connections from authorized IPs Authorized IP address to access MTX-Tunnel All phone numbers are forbidden IP to phone which made a missed call or “on” text SMS Authorized phone number 1 Authorized phone number 2 Prefix for local incoming calls (doesn’t include prefix)

Details:

• GPRS_timeout: 10” This parameter makes the 3G connection activate itself after the missed call or incoming SMS with “on” text string but stop after10 minutes without 4G-serial data traffic
• As an example, if the data is transferred in 30 minutes then the connection will be closed after another 10 minutes, giving a total of 40 minutes