-/** The sender subcommands. */
-enum {SENDER_ADD, SENDER_DELETE, SENDER_ALLOW, SENDER_DENY, SENDER_ON, SENDER_OFF, NUM_SENDER_CMDS};
+/**
+ * A little preprocessor fu helps to create the sender_subcommand enumeration
+ * below and the list of sender name strings without duplicating the commands.
+ */
+#define SENDER_SUBCOMMANDS \
+ SENDER_SUBCOMMAND(add) /**< Add a target (udp only). */ \
+ SENDER_SUBCOMMAND(delete) /**< Delete a target (udp only). */ \
+ SENDER_SUBCOMMAND(allow) /**< Allow connections from given IP address(es). */ \
+ SENDER_SUBCOMMAND(deny) /**< Deny connections from given IP address(es). */ \
+ SENDER_SUBCOMMAND(on) /**< Activate the sender. */ \
+ SENDER_SUBCOMMAND(off) /**< Deactivate the sender. */ \
+
+/** Concatenate "SENDER_" and the given arg and append a comma. */
+#define SENDER_SUBCOMMAND(_name) SENDER_ ## _name,
+
+/**
+ * Each sender subcommand gets an SENDER_xxx identifier. The identifier is
+ * passed from the sender command handler to the server process via shared
+ * memory.
+ */
+enum sender_subcommand {
+ SENDER_SUBCOMMANDS /**< List of SENDER_xxx identifiers. */
+ NUM_SENDER_CMDS /**< Used as array size in struct \ref sender. */
+};
+
+#undef SENDER_SUBCOMMAND
+
+/**
+ * Redefine it to expand to the stringified name of the sender so that
+ * SENDER_SUBCOMMANDS above now expands to the comma-separated list of sender
+ * name strings. This is used in command.c to define and initialize an array of
+ * char pointers.
+ */
+#define SENDER_SUBCOMMAND(_name) #_name,