modbus_set_error_recovery - set the error recovery mode
int modbus_set_error_recovery(modbus_t *ctx,
function shall set the error recovery
mode to apply when the connection fails or the byte received is not expected.
The argument error_recovery
may be bitwise-or’ed with zero or
more of the following constants.
By default there is no error recovery (MODBUS_ERROR_RECOVERY_NONE) so the
application is responsible for controlling the error values returned by
libmodbus functions and for handling them if necessary.
When MODBUS_ERROR_RECOVERY_LINK is set, the library will attempt an reconnection
after a delay defined by response timeout of the libmodbus context. This mode
will try an infinite close/connect loop until success on send call and will
just try one time to re-establish the connection on select/read calls (if the
connection was down, the values to read are certainly not available any more
after reconnection, except for slave/server). This mode will also run flush
requests after a delay based on the current response timeout in some
situations (eg. timeout of select call). The reconnection attempt can hang for
several seconds if the network to the remote target unit is down.
When MODBUS_ERROR_RECOVERY_PROTOCOL is set, a sleep and flush sequence will be
used to clean up the ongoing communication, this can occurs when the message
length is invalid, the TID is wrong or the received function code is not the
expected one. The response timeout delay will be used to sleep.
The modes are mask values and so they are complementary.
It’s not recommended to enable error recovery for slave/server.
The function shall return 0 if successful. Otherwise it shall return -1 and set
errno to one of the values defined below.
The value of the argument error_recovery is not
The libmodbus documentation was written by Stéphane Raimbault