/// <summary>
        /// IM SDK 初始化。
        /// </summary>
        /// <param name="sdk_app_id"></param>
        /// <param name="json_sdk_config"></param>
        /// <returns></returns>
        [DllImport(@"imsdk.dll", CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
        public extern static int TIMInit(long sdk_app_id, string json_sdk_config);

        /// <summary>
        /// 登录
        /// </summary>
        /// <param name="user_id">用户id</param>
        /// <param name="user_sig">签名</param>
        /// <param name="cb"></param>
        /// <returns></returns>
        [DllImport(@"imsdk.dll", CallingConvention = CallingConvention.Cdecl)]
        private extern static int TIMLogin(string user_id, string user_sig, TIMCommCallback cb);

        /// <summary>
        /// 接收新消息回调
        /// </summary>
        /// <param name="cb"></param>
        [DllImport(@"imsdk.dll", CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
        private extern static void TIMAddRecvNewMsgCallback(delegateTIMRecvNewMsgCallback cb);

        public void ImInit()
        {
            int sdk_app_id = 1400000000;
            var data = new { sdk_config_log_file_path = AppDomain.CurrentDomain.BaseDirectory, sdk_config_config_file_path = AppDomain.CurrentDomain.BaseDirectory };
            TIMInit(sdk_app_id, JsonConvert.SerializeObject(data));
            TIMAddRecvNewMsgCallback(TIMRecvNewMsgCallback);
            var tLSSig = new TLSSigAPIv2(sdk_app_id, "163250645178b565ffc0b22618d14a88d8a91d86f0e76813313197a5xxxxxxx");
            TIMLogin("用户", tLSSig.GenSig("用户"), CommCallback);

        }
        private delegate int TIMCommCallback(int code, string desc, string json_params);
        
        private int CommCallback(int code, string desc, string json_params)
        {
            return code;
        }
        private delegate void delegateTIMRecvNewMsgCallback(string json_msg_array,IntPtr user_data);
        private  void TIMRecvNewMsgCallback(string json_msg_array, IntPtr user_data) {
            var b = Encoding.Default.GetBytes(json_msg_array);
            richTextBox1.AppendText(Encoding.UTF8.GetString(b));
        }

        private void Form1_Load(object sender, EventArgs e)
        {
          ImInit();
        }