微信小程序使用websocket通讯的demo，含前后端代码，亲测可用

App({
  globalData: {
  socketStatus: 'closed',
  },
 onLaunch: function() { 
  var that = this;
  if (that.globalData.socketStatus === 'closed') {
    that.openSocket();
  }
 }
 openSocket() {
  //打开时的动作
  wx.onSocketOpen(() => {
   console.log('WebSocket 已连接')
   this.globalData.socketStatus = 'connected';
   this.sendMessage();
  })
  //断开时的动作
  wx.onSocketClose(() => {
   console.log('WebSocket 已断开')
   this.globalData.socketStatus = 'closed'
  })
  //报错时的动作
  wx.onSocketError(error => {
   console.error('socket error:', error)
  })
  // 监听服务器推送的消息
  wx.onSocketMessage(message => {
   //把JSONStr转为JSON
   message = message.data.replace(" ", "");
   if (typeof message != 'object') {
   message = message.replace(/\ufeff/g, ""); //重点
   var jj = JSON.parse(message);
   message = jj;
   }
   console.log("【websocket监听到消息】内容如下：");
   console.log(message);
  })
  // 打开信道
  wx.connectSocket({
   url: "ws://" + "localhost" + ":8888",
  })
  },
 //关闭信道
  closeSocket() {
  if (this.globalData.socketStatus === 'connected') {
   wx.closeSocket({
   success: () => {
    this.globalData.socketStatus = 'closed'
   }
   })
  }
  },
  //发送消息函数
  sendMessage() {
  if (this.globalData.socketStatus === 'connected') {
  //自定义的发给后台识别的参数 ，我这里发送的是name
   wx.sendSocketMessage({
   data: "{\"name\":\"" + wx.getStorageSync('openid') + "\"}" 
   })
  }
  },
})

 org.java-websocket
 Java-WebSocket
 1.3.0

 /**
  * 启动websocket
  */
 public void startWebsocketInstantMsg() {
  WebSocketImpl.DEBUG = false;
  MyWebScoket s;
  s = new MyWebScoket(8888);
  s.start();
  System.out.println("websocket启动成功");
 }

import com.alibaba.fastjson.JSONObject;
import org.java_websocket.WebSocket;
import org.java_websocket.handshake.ClientHandshake;
import org.java_websocket.server.WebSocketServer;
import java.net.InetSocketAddress;
import java.net.UnknownHostException;
import java.util.Map;
public class MyWebScoket extends WebSocketServer {
 public MyWebScoket() throws UnknownHostException {
  super();
 }
 public MyWebScoket(int port) {
  super(new InetSocketAddress(port));
 }
 public MyWebScoket(InetSocketAddress address) {
  super(address);
 }
 @Override
 public void onOpen(WebSocket conn, ClientHandshake handshake) {
  // ws连接的时候触发的代码，onOpen中我们不做任何操作
 }
 @Override
 public void onClose(WebSocket conn, int code, String reason, boolean remote) {
  //断开连接时候触发代码
  userLeave(conn);
  System.out.println(reason);
 }
 @Override
 public void onMessage(WebSocket conn, String message) {
  //有用户连接进来
  Map obj = (Map) JSONObject.parse(message);
  System.out.println(message);
  String username = obj.get("name");
  userJoin(conn, username);
 }
 @Override
 public void onError(WebSocket conn, Exception ex) {
  //错误时候触发的代码
  System.out.println("on error");
  ex.printStackTrace();
 }
 /**
  * 去除掉失效的websocket链接
  */
 private void userLeave(WebSocket conn){
  WsPool.removeUser(conn);
 }
 /**
  * 将websocket加入用户池
  * @param conn
  * @param userName
  */
 private void userJoin(WebSocket conn,String userName){
  WsPool.addUser(userName, conn);
 }
}

import com.td.yousan.util.StringUtils;
import org.java_websocket.WebSocket;
import java.util.*;
public class WsPool {
 private static final Map wsUserMap = new HashMap();
 /**
  * 通过websocket连接获取其对应的用户
  */
 public static String getUserByWs(WebSocket conn) {
  return wsUserMap.get(conn);
 }
 /**
  * 根据userName获取WebSocket,这是一个list,此处取第一个
  * 因为有可能多个websocket对应一个userName（但一般是只有一个，因为在close方法中，我们将失效的websocket连接去除了）
  */
 public static WebSocket getWsByUser(String userName) {
  Set keySet = wsUserMap.keySet();
  synchronized (keySet) {
   for (WebSocket conn : keySet) {
    String cuser = wsUserMap.get(conn);
    if (cuser.equals(userName)) {
     return conn;
    }
   }
  }
  return null;
 }
 /**
  * 向连接池中添加连接
  */
 public static void addUser(String userName, WebSocket conn) {
  wsUserMap.put(conn, userName); // 添加连接
 }
 /**
  * 获取所有连接池中的用户，因为set是不允许重复的，所以可以得到无重复的user数组
  */
 public static Collection getOnlineUser() {
  List setUsers = new ArrayList();
  Collection setUser = wsUserMap.values();
  for (String u : setUser) {
   setUsers.add(u);
  }
  return setUsers;
 }
 /**
  * 移除连接池中的连接
  */
 public static boolean removeUser(WebSocket conn) {
  if (wsUserMap.containsKey(conn)) {
   wsUserMap.remove(conn); // 移除连接
   return true;
  } else {
   return false;
  }
 }
 /**
  * 向特定的用户发送数据
  */
 public static void sendMessageToUser(WebSocket conn, String message) {
  if (null != conn && null != wsUserMap.get(conn)) {
   conn.send(message);
  }
 }
 /**
  * 向所有用户名中包含某个特征得用户发送消息
  */
 public static void sendMessageToSpecialUser(String message,String special) {
  Set keySet = wsUserMap.keySet();
  if (special == null) {
   special = "";
  }
  synchronized (keySet) {
   for (WebSocket conn:keySet) {
    String user = wsUserMap.get(conn);
    try {
     if (user != null) {
      String [] cus = user.split("_");
      if (!StringUtils.isNullOrEmpty(cus[0])) {
       String cusDot = "," + cus[0] + ",";
       if (cusDot.contains(","+special+",")) {
         conn.send(message);
       }
      }else {
       conn.send(message);
      }
     }
    }catch (Exception e) {
     e.printStackTrace();
     //wsUserMap.remove(conn);
    }
   }
  }
 }
 /**
  * 向所有的用户发送消息
  */
 public static void sendMessageToAll(String message) {
  Set keySet = wsUserMap.keySet();
  synchronized (keySet) {
   for (WebSocket conn : keySet) {
    String user = wsUserMap.get(conn);
    if (user != null) {
     conn.send(message);
    }
   }
  }
 }
}