UDP Scan Devices in LAN

• First, open a UDP receiving port on the desktop.

• Then send the following UDP broadcast to port 46953 in the LAN:

  {"ip":"desktop ip address","port":50000} // port is the desktop listening port

• The device will reply to the desktop's receiving port with:

  {
      "ip":"192.168.31.99",
      "port":"46952",
      "devname":"Device Name",
      "deviceid":"123456789012345678901234567890123456790", // device UDID
      "devsn":"XXXXXXXXXXXX",                               // device serial number
      "devmac":"02:03:04:05:06:07",                         // device Wi‑Fi MAC address
      "devtype":"iPhone8,1",                                // device model
      "zeversion":"0.0.1.738",                              // service version
      "sysversion":"9.0.2"                                  // iOS version
  }

• Desktop UDP scan example (Python 3.x):

  # -*- coding: utf-8 -*-
  import socket
  import json
  
  local_ip = '192.168.31.13'  # desktop IP address
  local_port = 31500
  
  local = (local_ip, local_port)
  remote = ("255.255.255.255", 46953)
  s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
  s.bind(local)
  
  s.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)
  s.sendto(json.dumps({"ip": local_ip, "port": local_port}).encode('utf-8'), remote)  # encode as UTF-8
  
  while True:
      data, addr = s.recvfrom(2048)
      if not data:
          print("client has exist")
          break
      print("received:", data, "from", addr)
  
  s.close()

• Desktop UDP scan example (Node.js):

  const http = require('http');
  const dgram = require('dgram');
  
  const server_Port = 31500;  // UDP receive port
  const client_Port = 31501;  // UDP send port
  
  const device_List = {};     // device list
  
  // UDP server (receive)
  const server_Socket = dgram.createSocket('udp4');
  server_Socket.on('message', function(msg, rinfo){
      console.log('received: %s', msg);
      const device_Info = JSON.parse(msg);
      if (device_Info.deviceid) {
          device_List[device_Info.deviceid] = device_Info; // de-duplicate by deviceid
      }
  });
  server_Socket.bind(server_Port);
  
  // UDP client (send)
  const client_Socket = dgram.createSocket('udp4');
  client_Socket.bind(client_Port);
  
  function search(){
      const server_List = [];
      const os = require('os');
      const ifaces = os.networkInterfaces();
      for (const dev in ifaces) {
          ifaces[dev].forEach(function(details){
              if (details.family === 'IPv4') {
                  server_List.push(details.address);
              }
          });
      }
      for (const address of server_List) {
          const ip_ar = address.split(".");
          const send2ip = `${ip_ar[0]}.${ip_ar[1]}.${ip_ar[2]}.255`;
          const client_Socket = dgram.createSocket('udp4');
          const msg = JSON.stringify({ip: address, port: server_Port});
          client_Socket.send(msg, 0, msg.length, 46953, send2ip);
      }
  }
  
  http.createServer(function (request, response) {
      response.writeHead(200, {'Content-Type': 'application/json'});
      search();
      response.end(JSON.stringify(device_List));
  }).listen(22222);
  
  search();
  console.log('Web service at: http://127.0.0.1:22222/');