When GPL operates as a MODBUS master, it sets up a TCP client connection with a remote MODBUS/TCP slave. The slave acts as a TCP server. When the connection is no longer needed, it may be closed. To establish a connection, follow this procedure:
| Step | Action |
|---|---|
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1. |
Create an IPEndPoint object for the remote MODBUS/TCP slave. This object normally specifies the IP address of the slave and omits the port number, in which case the standard MODBUS/TCP port is used. |
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2. |
Create a Modbus object using this endpoint_object. Creating a Modbus object does not establish a connection, but simply saves the endpoint information for later. |
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3. |
Use the modbus_object.Timeout property to set an appropriate timeout value for the connection. By default the timeout is infinite. |
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4. |
Use the various Modbus class methods to read or write data. The first time you issue a read or write, GPL attempts to connect with the MODBUS slave. If the slave does not respond, an exception is thrown. |
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5. |
When finished with the MODBUS slave, call modbus_object.Close to close it. Do this at the end of a session, not after each read or write request. |