Determine whether the currently requested network is internal or external

1. Scene analysis

There's a need recently , There is a function that can only be used by Internet users , Intranet users have no feelings , And in the same reference , Then I need to initialize , For current users IP Judge , Look at this. IP Can I access the intranet

2. The front-end implementation

The front-end implementation is just one idea , use AJAX Call a data or interface that only the Intranet can access . If I run out of time , Then it's the Internet .

// Code body 
ping = (address,callback) =>{
    
  var img = new Image();
  var start = new Date().getTime();
  // An intranet picture   Used to judge the network type   This picture cannot be loaded on the Internet 
  img.src =address+"?time="+start;
  var flag = false;
  img.onload = function(){
    
    flag = true;
    // stay 2 Seconds   Load out the picture   Then it will be regarded as the intranet 
    console.log(" Intranet ")
  }
  var timer = setTimeout(function(){
    
      if(!flag){
    
        flag = false;
        if (callback && typeof callback == 'function') callback();
      }
  },2000);
}
// Use the callback function to trigger our event 
 this.ping("http://neiwang.com/static/img/4345wee68dsfsd.png",()=>{
     
  // Only the Internet will execute this callback 
  alert(" I'm Internet ")
})

The code is simple , Just respond to our message before the timer arrives , That's intranet , But there is a serious risk
If the resource used to verify the intranet is deleted or the interface hangs , Then all of us IP Will be regarded as an external network , Because you are all overtime . Or if our network vibrates , Or the loaded resources are very large , It can also cause problems . So if you want to use this method, you must ensure , The resources or interfaces used for verification must be fast , Resources are guaranteed not to be deleted by mistake . It's best to write an interface or a small picture to judge the interface timeout . Don't choose any one for dozens M Pictures of the , In case the network explodes, it will be over .

3. The backend implementation

  public static boolean test() throws IOException {
    
        String ip = "apaddress";
        Runtime runtime = Runtime.getRuntime(); //  Get the running object of the current program 
        Process process = null; // Declare processing class objects 
        String line = null; // Return line information 
        InputStream is = null; // Input stream 
        InputStreamReader isr = null;//  Byte stream 
        BufferedReader br = null;
        boolean res = false;//  result 
        try {
    
            process = runtime.exec("ping " + ip); // PING
            is = process.getInputStream(); //  Instantiate the input stream 
            isr = new InputStreamReader(is);//  Convert the input stream into a byte stream 
            br = new BufferedReader(isr);//  Read text from bytes 
            while ((line = br.readLine()) != null) {
    
            	// Be sure to capitalize here   Because in linux In the system , It's lowercase   To be compatible with the system, add 
                if (line.toUpperCase().contains("TTL")) {
    
                    res = true;
                    break;
                }
            }
            if (res) {
    
                return true;
            } else {
    
                return false;
            }
        } catch (IOException e) {
    
            runtime.exit(1);
            return false;
        } finally {
    
            if (is != null) {
    
                is.close();
            }
            if (isr != null) {
    
                isr.close();
            }
            if (br != null) {
    
                br.close();
            }
        }
    }

Personally, I prefer to use the backend to realize , This only needs to be used IP that will do , No additional resources are required , More secure .

4. matters needing attention

If you use the back-end method, please pay attention , because java simulation PING request , If it doesn't work, it may cause a long-term jam , Because the way to get the request is while loop , There is a jam . So when calling this interface ,ajax Be sure to add the timeout . Avoid other problems caused by wireless waiting .
The reference codes are as follows ：

ipAddressPing = (ip,callback,timeout=2000)=>{
    
    $.ajax({
    
      url:'/api/demo/ipAddressPing?ipAddress='+ip,
      type:'get',
      timeout:timeout, // Set the timeout time 2s
      success:function(res){
    
        console.log(res)
        // The request did not time out , however PING no , It also shows that it is an external network   Need to call interface   Here you can judge for yourself 
        if (!res) {
     
          if (callback && typeof callback == 'function') callback(res);
        }
      },
      error:function(err){
    
        console.log(err)
        // Request timeout description   Extranet   Need to call interface 
        if (callback && typeof callback == 'function') callback(res);
      }
    })
  }