mbusd is open-source Modbus TCP to Modbus RTU (RS-232/485) gateway.

• Small footprint - suitable to run on embedded devices and SBCs like Raspberry Pi
• Multi-master - multiple TCP masters can access slave devices in RTU network using same gateway
• Robustness - can retry requests with mismatched response CRC
• Flexible RTU modes - speed/parity/stop-bits/timeouts can be configured for RTU network
• Support for both of automatic and manual (using RTS bit) direction control types for RS-485 transceivers

• 01: Read coil status
• 02: Read input status
• 03: Read holding registers
• 04: Read input registers
• 05: Force single coil
• 06: Preset single register
• 07: Read exception status
• 15: Force multiple coils
• 16: Preset multiple registers

Please note all other function codes (including vendor-specific extensions) are supported on a "best-effort" basis and most likely will fail.

$ git clone https://github.com/3cky/mbusd.git mbusd.git
$ cd mbusd.git
$ ./configure
$ make
# make install
$ make clean

   mbusd [-h] [-d] [-t] [-v level] [-L logfile] [-p device] [-s speed] [-m mode] \
   	       	[-P port] [-C maxconn] [-N retries] [-R pause] [-W wait] [-T timeout]

   -h     Usage help.
   -d     Instruct mbusd not to fork itself (non-daemonize).
   -t     Enable RTS RS-485 data direction control (if not disabled while compile).
   -v level
          Specifies  log  verbosity level (0 for errors only, 1 for warnings
          and 2 for also information messages.) If mbusd was compiled in debug mode,
          valid log levels are up to 9, where log levels above 2 forces
          logging of information about additional internal events.
   -L logfile
          Specifies log file name ('-' for logging to STDOUT only, default is /var/log/mbusd.log).
   -p device
          Specifies serial port device name.
   -s speed
          Specifies serial port speed.
   -m mode
          Specifies serial port mode (like 8N1).
   -P port
          Specifies TCP port number (default 502).
   -C maxconn
          Specifies maximum number of simultaneous TCP connections.
   -N retries
          Specifies maximum number of request retries (0 disables retries).
   -R pause
          Specifies pause between requests in milliseconds.
   -W wait
          Specifies response wait time in milliseconds.
   -T timeout
          Specifies connection timeout value in seconds (0 disables timeout).

Please note running mbusd on default Modbus TCP port (502) requires root privileges!

Please file issue with attached debug log in verbose (-v9) mode, i.e.:

   # mbusd -L/tmp/mbusd.log -p /dev/ttyUSB0 -s 9600 -P 502 -d -v9

Unless you were prompted so or there is another pertinent reason (e.g. GitHub fails to accept the bug report), please do not send bug reports via personal email.

1. Fork it and clone forked repository
2. Create your feature branch (git checkout -b my-new-feature)
3. Make your changes
4. Commit your changes (git commit -am 'Add some feature')
5. Push to the branch (git push origin my-new-feature)
6. Create new Pull Request

Victor Antonovich ([email protected])

Andrew Denysenko ([email protected]):

• RTS RS-485 data direction control
• RTU response receiving by length

This project is distributed under the BSD license. See the LICENSE file for the full license text.