From the SourceForge tracker:
I am using version hamlib-1.2.15.2~rc3. Start rigctl and specify rig 2
(rigctld). The command "s" (get_split_vfo) will return two parameters,
the spilt state (0 or 1) and the TX VFO name. The command "S"
(set_split_vfo) will send one parameter, the TX VFO name, but will not
send the split state (0 or 1). This is incorrect. In the file
dummy/netrigctl.c change netrigctl_set_split_vfo() line 782:
len = sprintf(cmd, "S %s\n", rig_strvfo(tx_vfo));
to include the "split" paramater; perhaps:
len = sprintf(cmd, "S %d %s\n", split, rig_strvfo(tx_vfo));
Thanks to Jim, N2ADR for reporting this.