Вопрос решен !
void client_status()
{
unsigned char number_client;
struct station_info *stat_info;
struct ip_addr *IPaddress;
IPAddress address;
int i=1;
number_client= wifi_softap_get_station_num(); // Count of stations which are connected to ESP8266 soft-AP
stat_info = wifi_softap_get_station_info();
Serial.print(" Total connected_client are = ");
Serial.println(number_client);
while (stat_info != NULL) {
IPaddress = &stat_info->ip;
address = IPaddress->addr;
Serial.print("client= ");
Serial.print(i);
Serial.print(" ip adress is = ");
Serial.print((address));
Serial.print(" with mac adress is = ");
Serial.print(stat_info->bssid[0],HEX);
Serial.print(stat_info->bssid[1],HEX);
Serial.print(stat_info->bssid[2],HEX);
Serial.print(stat_info->bssid[3],HEX);
Serial.print(stat_info->bssid[4],HEX);
Serial.print(stat_info->bssid[5],HEX);
stat_info = STAILQ_NEXT(stat_info, next);
i++;
Serial.println();
}