Modbus TCP Online Tool

Modbus TCP message parsing, command generation, and response generation tool, supporting MBAP header processing, multiple data types, and byte order conversion

Bug report

Browser execution mode: Your data is processed in your browser and is not uploaded to the server.

Speed and Stability: Processing speed depends on your device and browser. For large batch work, the desktop version may be more stable.

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If the online tool fails to load or run, try the desktop tool.https://tools.yikeaigc.com/

Tool Usage

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Set communication parameters first, then generate, parse, or batch process messages. This tool calculates hex messages, reads files, and packages results on this page. Batch files preview only the first 20; processing applies to all selected files.

Basic Communication Parameters

These settings are used as defaults for generation and parsing. After saving, they will be restored next time.

MBAP Header

Transaction Identifier Used to match requests and responses. Range: 0-65535.

Unit Identifier Used to map slave addresses in common gateway scenarios.

Transaction ID After Generation

Data Interpretation

Default Data Type

Default Byte Order

Default data start byte Standard read responses usually start at index 9.

Format & Check

Output format

Address Display

Modbus TCP uses the MBAP header and does not need CRC check. The protocol identifier is fixed at 0000, and the length field is calculated automatically.

Generate request, response, and exception frames

After switching the generation type, enter the matching parameters. The result will automatically split MBAP and PDU fields.

PDU Parameters

Function Code

Start Address

quantity

Write Value Coils accept 1/0, true/false, FF00/0000; registers use 0-65535.

Multi-value Write Separate multiple registers with commas or line breaks; use a 0/1 sequence for multiple coils.

Response Data Values Read responses are encoded using the default data type and byte order; for coil responses, enter a 0/1 sequence.

Exception Code

Description

Results

Set parameters first, then click “Generate Message”.

Transaction ID-

Length-

Unit ID-

features-

Parse Modbus TCP Message

Supports space-separated, continuous HEX, commas, and 0x prefixes. Add multiple rules to parse registers or float data.

Input & Rules

Hex packet

Data Parse Rules

Structure View

Waiting to parse

Transaction ID-

Protocol ID-

Length-

Unit ID-

Field	HEX	Decimal/Value	Description
Enter a message and click Parse.

#	Raw Bytes	Type	Byte order	Parsed value
Rule parsing results will appear here.

Batch Generate & Parse

Batch generate read commands, or paste multi-line messages or select multiple text files to parse. Results support CSV and ZIP downloads.

Batch Command Generation

Read Function Code

Quantity per Read

Start Address

End Address

Batch Message Parsing

Multi-line Messages

Choose text files File names will be used for result file names. Duplicates will get a number automatically.

#	Source	Transaction ID	Unit ID	Function Code	Parse data	Status
The first 20 batch parsing results will be shown.

Instructions

Software Usage Instructions

Set basic parameters: First set the transaction identifier, unit identifier, default data type, byte order, and data start byte. The transaction identifier is used to match requests and responses, while the unit identifier is commonly used by gateways to map slave addresses.
Generate Modbus TCP messages: Go to the “Generate Message” step, select request command, normal response, or exception response, then select the function code and enter the start address, quantity, write value, or response data. Click “Generate Message” to get the HEX result.
Parse a single message: Go to the “Parse Message” step and paste the hexadecimal message. The tool will break down the MBAP header, function code, data area, and exception code, and convert register values according to the parsing rules.
Configure data parsing rules: You can add multiple rules and set the start byte, data type, byte order, and quantity for each, used to parse registers, integers, or floating-point numbers at different positions.
Batch generate commands: Go to the “Batch Export” step, set the read function code, address range, and read quantity per command, generate multiple read commands with one click, and copy or download a TXT file.
Batch parse messages: Supports pasting multiple lines of messages, as well as selecting txt, csv, or log text files. Parsing results can be downloaded as CSV; when processing multiple files, a ZIP result package can be downloaded.
Save settings: Click “Save Settings” to save commonly used transaction ID, unit ID, data type, byte order, and output format for convenient future use.

FAQ

A: The MBAP header is 7 bytes in total and includes the transaction identifier, protocol identifier, length, and unit identifier. The protocol identifier is usually 0000, and the length field indicates the number of following bytes, including the unit identifier and PDU content.

A: The transaction identifier is used to match requests and responses, with a range of 0-65535. During continuous debugging, auto-increment can be enabled to make it easier to distinguish multiple communication results.

A: ABCD indicates standard big-endian order, DCBA indicates little-endian order, BADC indicates byte swapping within each 16-bit word, and CDAB indicates swapping the positions of two 16-bit words. The specific choice should be based on the device manual or on-site test results.

A: FLOAT32 uses 4 bytes, which is 2 registers. If the result is abnormal, you usually need to check the data start byte, register order, and byte order settings. A common approach is to switch between ABCD, DCBA, BADC, and CDAB, then compare the result with the device value.

A: A Modbus exception response adds 80H to the original function code. For example, the exception response for function code 03 is 83H. The following exception code indicates the cause, such as 01 illegal function, 02 illegal data address, 03 illegal data value, or 04 slave device failure.

A: In a standard read response, the MBAP header occupies 7 bytes, the function code occupies 1 byte, and the byte count field occupies 1 byte. Therefore, the actual data usually starts at byte 9, so enter 9 when counting from 0.

A: Text files such as txt, csv, and log are supported. It is recommended to put one Modbus TCP hexadecimal message per line. HEX can be space-separated, continuous characters, comma-separated, or in 0x-prefixed format.