Connection between GRDs and Middleware

Communication with Middleware uses a TCP/GPRS connection. To be able to establish the connection it is necessary to:

• Place the antenna correctly and ensure GPRS coverage.
• Place the SIM card, and, if necessary configure PIN.
• Configure correctly the cell phone operator for the establishment of the GPRS connection.
• Configure correctly the connection from the GRD-XF to the MW-XF
• Configure the GRD ID and password.
• Have a MW server running (read the "Intermediary Software - Middleware" section)

All TCP connections need a Server which awaits a connection request in a pre-established port and a client that, at the right time, will establish the connection to such server. The GRD-XF works as TCP clients, so we must have a Server (MW-XF) to wait for the connection request. We now explain how to configure the GRD-XF to establish communication with Exemys Middleware. We enter the MW-XF menu and configure the following parameters:

When this option is enabled, we tell the GRD to establish connection with the specified configuration. If this option is disabled the GRD-XF will not establish connections.

If you are using a GRD-XF-4G, you will be also be able to enable SSL encryption for the link between the GRD-XF and the MW.

If you use SSL mode please read the SSL certificate creation and installation appendix.

The IP address or URL of the server where the MW-XF running must be entered here. The GRD-XF can resolve URLs using DNS.

The server port must be entered in this field. The default port for the regular conexion is 40000. For SSL encryption the default port is 40001.

The GRD must be connected to a MW-XF, this is why it is absolutely necessary to place an ID number to identify the GRD-XF at the moment of connection and with a password if necessary.

If the GRD must establish a connection with the Middleware (MW), it has to be identified in order for the MW allows to remain connected. The GRD ID is part of this identification. If the MW has not configured such an ID as valid, it will close the connection with the GRD-XF, this is a number from 1 to 4000 and it must be unique.

The GRD equipment has a password for authentication with the MW, therefore, at the moment of connection the GRD-XF password is verified against the MW password, if there is a coincidence, the connection is accepted. Additionally, GRD-XF equipment can be configured and monitored through SMS messages. In the case of the configuration, it can be protected with a password. So when the SMS is sent, it must include the password to be able to make modifications. The password should have a maximum length of 8 characters.

Advanced:

This is the time the GRD-XF takes to decide that the connection with the MW has been closed.

This parameter defines how long will wait the GRD-XF to reboot if it can't establish a connection to the MW.

If connect the GRD-XF to Exemys Telemetry Server you don't need to read this section

The port in the MW must have the same configuration as the one in the GRD-XF, that is the TCP port through which the “GRD server“ connections are received. This port must be ready to receive connections, which means that it should not be blocked by any type of firewall or router.

Since MW 6.0.0 incomming SSL connections are allowed from GRD-XF-4G

We first create a GRD-XF with the same ID as the one loaded previously in the equipment, this is done from “Configuration -> GRDs” click on “New GRD”.

The password must be entered if there is one previously loaded in the equipment, otherwise, it should be kept blank.

The “Telephone” and “Description” parameters are optional, these help the user with the identification of the GRD-XF beyond the ID.

As to the "Serial port mode” we select as an example “Not Configured”, this refers to the mode of operation of the GRD-XF serial port, in this case it will not be used.

The 2 operational modes will be detailed later, as at the moment we just want to establish the connection between the GRD and the MW.

To verify whether the entered configuration into the GRD-XF is the correct one we have the possibility of monitoring the status of the connections and the signal.

To access the monitoring screen of the configurator click on the “Monitor” button. Then, the following screen will be displayed:

From here, the following parameters related to the connection are of interest: “Signal, SIM State, GPRS State and Link State”.

It indicates the signal level in dBm, the minimum value is -113 dBm, data transmission is impossible at this value.

Use this chart as reference for signal qualtity.

• Disabled: The SIM (Chip) is disabled from the GRD-XF configuration.

• Attaching: It is being registered in the GSM network.

• Selected but not resent: In models with SIM detection it indicates that the SIM is not placed.

• Pin Required: This message appears when a SIM card requires a PIN.

• PIN Error: This message shows that the PIN entered is incorrect.

• SIM Blocked: The SIM card is blocked, to be able to enable it you must enter its PUK. This operation is not possible using a GRD, and you will need a cell phone or another device to release the card.

• Low Signal: The signal level is insufficient.

• Ready: It is registered in the network.

The following are the possible states of the GPRS connection.

• Disabled: The GPRS connection is disabled in the GRD configuration.

• Waiting SIM Ready: The GPRS connection is disabled but is waiting for the equipment to register a GSM.

• Connecting: Is in the process of connection.

• Connected: Successful connection to GPRS.

• Error: Error in the connection to GPRS, it will retry in 30 seconds.

The TCP connection state can also be monitored. Remember that to be able to establish such a connection, you must count first on a GPRS service.
Once the GPRS connection is established, the possible TCP connection states are:

• Disabled: The TCP connection has net been enabled. In this state the Link LED is off.

• Waiting GPRS Ready: The connection to the MW (TCP) is enabled but is waiting for the equipment to connect to the GPRS to initiate it.

• Connecting: The GRD is attempting to establish a connection to the indicated IP address and port. If the GRD is not able to establish the TCP connection, the length of time in this state might be an indication of a failure. If it remains in this state for a few seconds (less than 10), it might be trying a connection to a closed port. If it maintains the state during a minute or more it might be attempting to connect to a port and/or IP behind a firewall and is being filtered.

• Connection Failed, Host Unreachable and Connection Refused: The 3 states imply that the connection to the MW was not possible, but individually, they indicate the reason why they occurred.
  In general, each one has a specific motive although it depends on the TCP connection on the server side for the indication to be correct, even so, any of the these 3 errors indicate a problem in the TCP connection.

• Connection Failed: This error appears when a connection to the configured IP is not possible.
• Host Unreachable: This happens when a connection to the IP is possible the port is open, through the router or firewall, but there is nothing connected to that port. 
• Connection Refused: In this case the connection cannot be established because the configured port is closed, this could happen because a router or firewall are blocking it. 

• Host Closed Connection: This is an event that happens when the server closes the connection. This could be because the MW service has stopped, the server turned off, the connection to Internet dropped or any motive by which the server loses connectivity.

• Logging in : The TCP connection has been established, and the GRD is going through the authentication process.

• Connected:The TCP connection has been established, at this time the GRD registers in the MW, if the ID and password are valid, the connection is maintained.

• DNS Failure : The GRD can't convert the URL into an IP address. Check if the IP address is OK.

• Error:  The event occurs if the connection was not completed after a certain time and no other type of failure was reported.

GRDs connected to the MW can be monitored, this can be done by accessing “Monitor -> GRDs Connected” , a list will be displayed showing all GRDs added to the MW ordered by ID, and showing if it is connected and if it is so it will show its IP.

Statistics are made based on the quantity of information received and transmitted. The information given by these statistics differ according to how the GRD type was defined.
To have access to statistics of each GRD the button located in the statistics column must be pressed.
When the GRD shows the serial port mode as “NOT CONFIGURED”, we will not be able to access the statistics.

The Modbus statistics screen is shown below:

When the GRD is connected the windows is displayed as enabled, on the contrary if the GRD is disconnected the Windows is shown in grey as disabled.
The window shows the number of packets sent to the GRD and received from it, those queries sent that are unanswered are part of the Timeout count.
The erase button resets the counters to zero.

The transparent mode statistics screen is shown below.

When the GRD is connected and a user is connected to the MW pointing to that GRD, the screen will be shown as enabled. 
In the statistics of the TR  mode we can find the name of the user and the IP to which he is connecting, as well as the  number of bytes transmitted to the serial port of the GRD and bytes received from the serial port of the GRD.
The erase button resets again the counters to zero.

2022-03-18