3. CIU 260 is now ready for a client, for example the SCADA system, to establish a socket connection and begin TCP/IP data exchange.
When a client connects CIU 260, the connection state will change to "Connected", and the cellular connection status LED1 indicates when
data transfer takes place.
When no data is being transferred, the connection states "Attached", "Context active" and "Connected".
All show the same LED1 status (short pulse).
A client, for example SCADA, establishes connection to CIU 260 by specifying the IP address and the TCP port 502. Data transfer is always
initiated from the client in the form of a Modbus TCP telegram embedded in a TCP/IP frame and directed to TCP port 502. To the client
software, the connection to CIU 260 is completely transparent.
The protection against unauthorised data access is high. The access to the APN network from the Internet can only take place via the VPN
tunnel. Moreover, data transfer requires a Modbus master client, knowledge of the Modbus functional profile and the use of a SCADA PIN
code, if enabled.
CIU 260 supervises the APN connection to ensure that it is still working. An automatic procedure ensures restarting of CIU 260 and repetition
of the APN connection sequence in case a deadlock situation has occurred. It also closes down socket connections that are left open by the
client and unused for more than 24 hours.
It is possible to use SMS communication while data communication is active. However in the "Connected" state, the delay time between
reception and reply increases.
A total of three Modbus clients can be connected to the Modbus TCP port of CIU 260 and communicate simultaneously. Each connection,
called a socket connection, is handled independently. If all three sockets are used simultaneously, a "Silence time-out" of only one minute is
used to prevent a complete occupation for a long time.
TM047309
Data connection directly from a PC to CIU 260
Pos. Description
1 PC Tool, etc.
2 "Static" IP address
3 Cellular network
4 Base station APN
5 CIU 260 with CIM 260 and SIM card
6 Cellular network
7 Setup, status and control commands via SMS
8 Mobile phone
TM047129
Cellular connection via VPN tunnel
36
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