1. 先在app.js 中声明并初始化以下

startWebSocket: function () {
var that = this;
    that.WebSocketInit()
      wx.onSocketError(function () {
    })
    wx.onSocketMessage(function (data_) {
      that.socketOperation(data_)
    })
    wx.onSocketClose(function (res) {
      that.WebSocketInit()
    })
  },
//连接websocket
  WebSocketInit: function () {
    wx.connectSocket({
      url: this.data.wws,
      data: {},
      method: 'GET',
      success: function (res) {
        console.log("connectSocket 成功")
      },
      fail: function (res) {
        console.log("connectSocket 失败")
      }
    })
    wx.onSocketOpen(function () {
      // callback
      var mCmd = { "cmd": "connect.Connect", "data": {} }
      wx.sendSocketMessage({
        data: JSON.stringify(mCmd),
        success: function (res) {
          console.log("sendSocketMessage 成功")
        },
        fail: function (res) {
          console.log("sendSocketMessage 失败")
        }
      });
wx.onSocketMessage(function (data) {
        console.log("onSocketMessage ", data)
      })
    })
},

2. 然后在新建一个辅助js来发送和接收数据

function sendMessage() {
  var mCmd = { "cmd": "connect.getWlList", "data": { "mdd": "370600" } }
  wx.sendSocketMessage({
    data: JSON.stringify(mCmd),
    success:function(res){
    }
  })
}
function resiverMessage(context) {
  wx.onSocketMessage(function (data) {
    context.onMessage(JSON.parse(data.data)) //这里定义一个onMessage方法，用于每个页面的回调
  })
 } module.exports = { 
    formatNumber: formatNumber, 
    judge: judge, 
    sendMessage: sendMessage, 
    resiverMessage: resiverMessage 
}

3. 使用的话也很简单

onMessage: function (res) {
    this.setData({ data: res.data });
    console.log(res);
  },
  onLoad: function (options) {
    app.data.util.sendMessage();
    app.data.util.resiverMessage(this)
}