Port Server for Port Sharing

You can install the port server software on a Geo SCADA Expert server or remote PC to enable a single port to be used for communications using multiple protocols. This is especially useful on devices on which there are a limited number of ports available.

There are two topologies for port sharing:

• Geo SCADA Expert server using port server for port sharing

  

• Remote PC using port server for port sharing

  

The port server setup for port sharing works as follows:

• The drivers in the Geo SCADA Expert server communicate with the Port Server software via a TCP/IP link. The TCP/IP link can be a connection to a remote PC that runs the Port Server software or can be a link within a Geo SCADA Expert server.
• The Port Server software enables a serial port on the Geo SCADA Expert server/remote PC to be used for communications with multiple protocols.
• The communication device that is connected to the port (such as a radio) is used to send and receive data to and from the outstations and other devices.
  

The port used for communicating via many different protocols is set to dynamic mode. This enables different Geo SCADA Expert drivers to communicate via a single serial port. For example, the DNP3 driver and Advanced Modbus drivers can both communicate via the same serial port even though they use different protocols.

When the port server receives data from an outstation or similar device via the serial port, it places the incoming data in a buffer. It then checks the incoming data for specific protocol signatures—when it recognizes the protocol, it sends the data to the relevant driver in the Geo SCADA Expert server via a TCP/IP connection. Similarly, when the port server receives data from a driver in the Geo SCADA Expert server, it places the data in a queue before sending the data to the relevant outstation. By default, there is a delay of 50ms between each message that is sent. This delay can be changed by altering the registry setting:

1. Access and Run a Registry Editor.

2. Use the Registry Editor to access the PortServer registry settings:

   HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Schneider Electric\ClearSCADA\PortServer

3. Change the InterMessageDelay.

To configure a port server for port sharing:

1. Install the Port Server Software.
2. In Geo SCADA Expert, configure a direct channel of the relevant type for each protocol that is to be used by the serial port. Configure the direct channels to have the following settings:
   • Connection Type is set to Remote Serial
   • Node Name is set to:
     • localhost (when the port server is installed on the Geo SCADA Expert server)
     • The name/address of the remote PC (when the port server is installed on a remote PC).
   • Port is set to the same port on each channel (this has to be the port that is to be shared)
   • Shared setting is enabled.

   You have to configure one channel per protocol and should apply the same settings to each of the channels (Baud Rate, Data Bits, and so on). The channels can be of any of the following protocols:

   • DNP3 (including WITS)
   • IEC 60870 (101 and 104)
   • Modbus ASCII
   • Modbus RTU (including Advanced Modbus, SCADAPack Modbus, and SCADAPack Realflo).

   For more information, see Create the Channels in the Database.