Solve the problem that esp8266 cannot connect mobile phones and computer hotspots

1、 Hardware platform

I'm using Esp8266 NodeMcu(Esp-12s)
2、 development environment
Arduino IDE
3、 Development board model selection

4、AP Pattern

#include <ESP8266WiFi.h> //  This program uses ESP8266WiFi library 
 
const char *ssid = "Fle"; // esp8266 The establishment of a wifi name 
                                  
 
const char *password = "gxd001213";  //esp8266 The establishment of a wifi password 
                                 
 
void setup() {
    
  Serial.begin(9600);              //  Start serial communication 
 
  WiFi.softAP(ssid, password);     //  This sentence is the key point .WiFi.softAP Used to start NodeMCU Of AP Pattern .
                                   //  There are two parameters in parentheses ,ssid yes WiFi name .password yes WiFi password .
                                   //  These two parameters are specific setup Define the position before the function .
 
  
  Serial.print("Access Point: ");    //  Output information through serial port monitor 
  Serial.println(ssid);              //  Tell the user NodeMCU Established by WiFi name 
  Serial.print("IP address: ");      //  as well as NodeMCU Of IP Address 
  Serial.println(WiFi.softAPIP());   //  By calling WiFi.softAPIP() You can get NodeMCU Of IP Address , Fixed for 192.168.4.1

}
 
void loop() {
     
}

5、STA Pattern

#include <ESP8266WiFi.h> //  This program uses ESP8266WiFi library 
 
const char* ssid     = "Fle";      //  Connect WiFi name （ Use mobile hotspot here Fle）
                                            
const char* password = "gxd001213";          //  Connect WiFi password 
                                           
                                            
void setup() {
    
  Serial.begin(115200);         //  Start serial communication 
  
  WiFi.begin(ssid, password);                  //  Start the network connection 
  Serial.print("Connecting to ");              //  The serial port monitor outputs network connection information 
  Serial.print(ssid); Serial.println(" ...");  //  Tell the user NodeMCU Is trying to WiFi Connect 
  
  int i = 0;                                   //  This program statement is used to check WiFi Whether the connection is successful 
  while (WiFi.status() != WL_CONNECTED) {
          // WiFi.status() The return value of the function is determined by NodeMCU Of WiFi Determined by the connection state . 
    delay(1000);                               //  If WiFi If the connection is successful, the return value is WL_CONNECTED 
    Serial.print(i++); Serial.print(' ');      //  Here through While Circulation NodeMCU Check every second WiFi.status() Function return value 
  }                                            //  meanwhile NodeMCU Read the connection time of the monitor output through the serial port in seconds .
                                               //  This second reading is through the variable i Add it every second 1 To achieve .
                                               
  Serial.println("");                          // WiFi After successful connection 
  Serial.println("Connection established!");   // NodeMCU Will output through the serial port monitor " Successful connection " Information .
  Serial.print("IP address: ");             //  It will also output NodeMCU Of IP Address . This function is achieved by calling 
  Serial.println(WiFi.localIP());              // WiFi.localIP() Function to implement . The return value of this function is NodeMCU Of IP Address .
}
 
void loop() {
                                       
}

If there is a situation of waiting , hold AP Frequency band changed to ２.４GHZ, Looks like Esp8266 I won't support it 5GHZ Frequency band .