+/** Adds a socket to the event system.
+ * @param[in] sock Socket event generator to use.
+ * @param[in] call Callback function to use.
+ * @param[in] data User data pointer for the generator.
+ * @param[in] state Current socket state.
+ * @param[in] events Event interest mask for connected or connectionless sockets.
+ * @param[in] fd &Socket file descriptor.
+ * @return Zero on error, non-zero on success.
+ */