点击发送按钮触发，消息发不出去
controller：

var ws = new WebSocket("ws://121.43.160.149:8890/ws/phone/message");
        var chatMessage = {
            messagetxt : $scope.mmm,
            touserid : thisId
        }
        var sMsg = {
            messageContext : chatMessage,
            messageType : "friendChat"
        }
        console.log(sMsg);
        ws.onopen = function(e){
            ws.send(JSON.stringify(sMsg));
        }

请问angularjs在用webSocket时应该怎么用？