What is mbusd?

This gateway connects Modbus TCP clients to RTU serial devices, acting as a TCP server that becomes an RTU master on the serial bus. Multiple TCP clients can share the same RS-232 or RS-485 line. Serial parameters like baud rate, parity, and timeouts are fully configurable. It handles RS-485 direction control automatically or via RTS, and can discard local echo from adapters that loop back transmissions. Standard function codes 1-7, 15, and 16 are supported; others work best-effort. Deployment options include building from source with CMake, running as a systemd service, or using the Docker image. The default port 502 needs root access. Settings come from command-line flags or a config file.

Should you self-host mbusd?

mbusd scores 52/100 on selfhost.directory (how scoring works) and ranks #3 of 4 in Industrial IoT. It has 684 GitHub stars.

It shipped 1 stable release in the past year. The latest, v0.5.3, came out on 7 April 2026.

Setup is moderate: expect some configuration beyond a single command. An official Docker image is available. It is BSD-3-Clause-licensed and written mostly in C.

Its closest alternative on selfhost.directory is LinuxCNC (63/100, 2 512 stars). It scores higher overall, so compare the two before you pick. See mbusd vs LinuxCNC side by side.