# Using Modbus Master and ModbusEthernet\_04.lib at the same time

**URL:** <https://www.wago.community/t/using-modbus-master-and-modbusethernet-04-lib-at-the-same-time/2900>\
**Category:** CODESYS\
**Created:** [October 6, 2026, 8:55am UTC](https://www.wago.community/t/using-modbus-master-and-modbusethernet-04-lib-at-the-same-time/2900 "2026-10-06T08:55:36Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Yevhen\_ea](https://avatars.discourse-cdn.com/v4/letter/y/a6a055/32.png) [@Yevhen\_ea](https://www.wago.community/u/Yevhen_ea)\
**Post date:** [October 6, 2026, 8:55am UTC](https://www.wago.community/t/using-modbus-master-and-modbusethernet-04-lib-at-the-same-time/2900/1 "2026-10-06T08:55:36Z")

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Hi, on Wago 750-890 & Codesys 2.3, I met the following issue:

I needed specific config to make 750-… a modbus tcp server on its reserved I/O memory range, so I sw off the internal Modbus Server on 502 port and used ModbusEthernet\_04.lib - this works fine.

But after configuring internal PLC config Modbus Master (I needed to access slaves too), it turned out a conflict between the function names in this library and Modbus Master generated code

 ![conflicting_libraries_eth_mb_04](https://us1.discourse-cdn.com/flex016/uploads/wago/original/2X/6/6ac2f04dadab5c6255c2bc324a0f059f429f8e8d.png)

Any ways to fix the issue? Or using the ETH\_MB\_MASTER from this library is the only solution?

Thanks,