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Protocol & FramingModbus Term

Modbus TCP

Modbus protocol encapsulated over a standard TCP/IP Ethernet connection.

Definition

Modbus TCP wraps the standard Modbus PDU in a 6-byte MBAP header and transmits it over a TCP/IP connection (default port 502). Because TCP handles error checking and retransmission, Modbus TCP drops the CRC-16 used in RTU. A single master can open multiple simultaneous TCP connections to different slaves, and many slave devices can accept connections from multiple masters.

Quick Facts

Default port502
HeaderMBAP (6 bytes)
Error checkTCP (no CRC)
ConnectionsMulti-master supported

Related Terms

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ModPackQT Modbus Glossary · Updated 2026