Glossary Updates12 new terms added to the glossaries · October 2, 2026, 22:44 CEST
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Glossary · Industrial communication

Modbus TCP

Also known as: Modbus TCP/IP, Modbus/TCP

German: Modbus TCP

In industrial communication, Modbus TCP is the variant of Modbus that transports Modbus requests and responses over TCP/IP, usually on TCP port 502. A seven-byte MBAP header precedes the Modbus function code and data, and a unit identifier addresses devices behind gateways.

  • Industrial communication
  • Standards

In one sentence

Modbus TCP carries Modbus requests over TCP/IP, typically on port 502, with an MBAP header in front of the Modbus data.

Example

A SCADA system reads the status registers of a solar inverter over Modbus TCP at address 192.168.10.20, port 502, unit ID 1.

How it applies

  • Engineering: Modbus TCP uses standard Ethernet infrastructure. Clients open TCP connections to servers; some devices allow only a few simultaneous connections, which limits how many systems can read them.
  • Integration: Gateways between Modbus RTU and Modbus TCP use the unit identifier to address the serial device behind them.
  • Security: Modbus TCP has no built-in authentication. Firewalls restrict port 502 to known clients; protocol-aware firewalls can block write function codes.
  • Documentation: The documentation team documents IP settings, port, supported function codes, maximum connections, Timeout behavior and the register map.

Modbus TCP vs. Modbus TCP/IP

Both names refer to the same protocol. "Modbus TCP/IP" emphasizes the TCP/IP stack; the Modbus Organization's specification is titled "Modbus Messaging on TCP/IP". Choose one name and use it consistently in documentation.

By knowledge.aitechdoc.world · Published September 26, 2026 · Last reviewed

Source: Modbus Organization, MODBUS Messaging on TCP/IP Implementation Guide V1.0b

Definitions follow the cited standards and specifications. Where a source is a copyrighted publication, such as an ISO, IEC or EN standard, the definition is a close paraphrase, not a verbatim quotation, so as not to infringe copyright. We recommend reading the original publication. The sections “How it applies” are editorial commentary by AI TechDoc Knowledge and are not part of any standard.

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