JQuery跨域调用webservice问题

页面JS代码如下：

方法一：

$.getJSON(

    "http://ip地址/chatService/chatService.asmx/userLogin?jsoncallback=?",

    {userId:"'"+$("#userId").val()+"'", serverId:"'"+$("#serverId").val()+"'", date:"'"+new Date()+"'"},

    function(json)

    {

       if(json.length > 0)

       {

           alert(json);                            }

       }

); 

方法二：

               $.ajax({

                    async: false，

                    type: "POST",

                    contentType:"application/json;utf-8",

                    url: "http://ip地址/chatService/chatService.asmx/userLogin?callback=?",

                    data: "{userId:'"+$("#userId").val()+"', serverId:'"+$("#serverId").val()+"', date:'"+ new Date() +"'}",

                    datatype:"json",

                    success: function(json){

                        if(json != "")

                        {

                            alert(json);

                        }

                    }

                });

web service方法

已经包含了[System.Web.Script.Services.ScriptService]



        [WebMethod]

        public void userLogin(string userId, string serverId, string date)

        {

            DBManager db = new DBManager("COM");

            SqlParameter[] p = new SqlParameter[4];

            p[0] = new SqlParameter("@userId", SqlDbType.Int, 0);

            p[0].Direction = ParameterDirection.Input;

            p[0].Value = userId;

            p[1] = new SqlParameter("@serverId", SqlDbType.Int, 0);

            p[1].Direction = ParameterDirection.Input;

            p[1].Value = serverId;

            p[2] = new SqlParameter("@date", SqlDbType.DateTime, 0);

            p[2].Direction = ParameterDirection.Input;

            p[2].Value = date;

            p[3] = new SqlParameter("@returns", SqlDbType.Int, 0);

            p[3].Direction = ParameterDirection.ReturnValue;



            int sysId = db.ExeProc("ap_webUserLog", p);

            string callback = HttpContext.Current.Request["jsoncallback"];

            string retV = "";

            retV += "({state:" + sysId + ", msg:'成功建立连接'})";

            HttpResponse response = HttpContext.Current.Response;

            response.Write(callback + retV);

            response.End();

        }

现在的问题是：
用方法一，则整个getJSON执行不到内部
用方法二，jquery库文件中j.open(G,M.URL, async)提示没有权限。
跨域问题网上也看了，搞了下还是没明白。故求教。