跨域请求

        byte[] bs = Encoding.UTF8.GetBytes(sendParam);
        HttpWebRequest req = (HttpWebRequest)HttpWebRequest.Create("http://服务端地址:8888/sms.aspx");
        req.Method = "POST";
        req.ContentType = "application/x-www-form-urlencoded";
        req.ContentLength = bs.Length;

        using (Stream reqStream = req.GetRequestStream())
        {
            reqStream.Write(bs, 0, bs.Length);
        }
        using (WebResponse wr = req.GetResponse())
        {
            StreamReader sr = new StreamReader(wr.GetResponseStream(), Encoding.Default);
            context.Response.Write(sr.ReadToEnd().Trim());
        }