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Kepware Knowledge Base: Solution

Unable to Connect to S7-200/300/400/1200 PLC via TCP/IP Ethernet

Last Update: 11/12/2018

When using the Siemens TCP/IP Ethernet Driver, KEPServerEX is unable to connect to an S7-200, 300, S7-400, or S7-1200 PLC.

1. Review suggestions that apply to all drivers using TCP. For more information, refer to No Tag Data via TCP using Ethernet-To-Serial Converter.

2. If the Channel Diagnostics of an S7-200/300/400/1200 device only display green (TX) text, users can adjust the Link Type or CPU Slot parameters (located in Device Properties | S7 Comm. Parameters). When doing so in Kepware's driver, disconnect all clients that are attempting to access the device in question from KEPServerEX. Then, re-open the server, make and save the changes, and reconnect the clients.

1. In the S7-200/300/400/1200 Industrial Ethernet protocol used by the Siemens TCP/IP Ethernet Driver, connections are divided into the following three types:

  • PC Connections (for general applications like KEPServerEX)
  • OP Connection (for a local HMI panel)
  • PG Connection (for programming the PLC)

The PLC has a limited number of each link type available. If one link type is unavailable, the additional connections must use other link types.

2. Depending on the settings in the PLC program, it may be necessary to set the driver's CPU Slot parameter to a value that is not the position in which the CPU physically resides.

3. For more information, refer to "S7-300/S7-400 Communications Parameters" located in the "S7 Communications Parameters" topic of the Siemens TCP/IP Ethernet Driver help file.