Allow rigctld to continue operating after tcp or serial rig disappears

tests/rigctl_parse.c

@@ -593,7 +593,11 @@ extern int vfo_mode;
 extern char send_cmd_term;
 int ext_resp = 0;
 unsigned char resp_sep = '\n';      /* Default response separator */
-
+/* Note that vfo_mode and ext_resp are not thread safe
+ * So to run either a vfo_mode or ext_resp mode rigctld it needs to be
+ * on a separate rigctld instance on a different port.  One port per vfo_mode/ext_resp combination for a maximum of 4 instances/ports to cover all 4 combos
+ * Significant rewrite to fix this for 1 instance
+ */
 
 int rigctl_parse(RIG *my_rig, FILE *fin, FILE *fout, char *argv[], int argc, sync_cb_t sync_cb)
 {
@@ -1564,6 +1568,7 @@ int rigctl_parse(RIG *my_rig, FILE *fin, FILE *fout, char *argv[], int argc, syn
 
     if (sync_cb) sync_cb (0);   /* unlock if necessary */
 
+    if (retcode == RIG_EIO) return retcode;
     if (retcode != RIG_OK)
     {
         /* only for rigctld */