libmodbus is a free software library to send/receive data according to the Modbus protocol. This library is written in C and supports RTU (serial) and TCP (Ethernet) communications.
The license of libmodbus is LGPL v2.1+ and the licence of programs in the tests directory is BSD 3-clause.
The documentation is provided with libmodbus releases as man pages (generated from doc sources). You can also browse the documentation of the different releases of libmodbus:Wiki for general informations.
modbus_t *mb; uint16_t tab_reg; mb = modbus_new_tcp("127.0.0.1", 1502); modbus_connect(mb); /* Read 5 registers from the address 0 */ modbus_read_registers(mb, 0, 5, tab_reg); modbus_close(mb); modbus_free(mb);