Wemos WIFI_AP_STA problem

#include <ESP8266WiFi.h>

char SSID_NAME[] = "AP_SSID_NAME";
char SSID_PASSWORD[] = "AP_SSID_PASSWORD";

const char *sta_ssid = "ROUTER_SSID_NAME";
const char *sta_password = "ROUTER_SSID_PASSWORD";

WiFiServer server(80);
IPAddress staticIP(192,168,1,20);
IPAddress gateway(192,168,1,1);
IPAddress subnet(255,255,255,0);

void setup() {
    Serial.begin(115200);
    WiFi.mode(WIFI_AP_STA);
    Serial.println("");
    Serial.print("Configuring access point...");

    int channel = 7;         // Channel : 1 - 13
    bool hidden=true;       // true / false
    int max_connection = 5;  // 0 - 8

    WiFi.softAP(SSID_NAME, SSID_PASSWORD, channel, hidden, max_connection);
    WiFi.softAPConfig(staticIP, gateway, subnet);

    Serial.println();
    Serial.print("Connecting to ");
    Serial.println(sta_ssid);
    WiFi.begin(sta_ssid, sta_password);

    while (WiFi.status() != WL_CONNECTED)
    {
        delay(500);
        Serial.print(".");
    }

    Serial.println("");
    Serial.println("WiFi connected");
    Serial.println("IP address: ");
    Serial.println(WiFi.localIP());

    server.begin();

    Serial.println();
    Serial.println("Server");
    Serial.print("IP: ");      Serial.println(WiFi.softAPIP());
    Serial.printf("MAC:%s\n",  WiFi.softAPmacAddress().c_str());
    Serial.print("Status: ");  Serial.println(WiFi.status());    // Network parameters
    Serial.print("IP: ");      Serial.println(WiFi.localIP());
    Serial.print("Subnet: ");  Serial.println(WiFi.subnetMask());
    Serial.print("Gateway: "); Serial.println(WiFi.gatewayIP());
    Serial.print("SSID: ");    Serial.println(WiFi.SSID());
    Serial.print("Signal: ");  Serial.println(WiFi.RSSI());
}

void loop()
{
    WiFiClient client = server.available();
    if (!client) {return;}

    String request = client.readStringUntil('\r');
    Serial.println("Answer from the station: " + request);

    client.flush();
}