我用AT指令集向串口发送命令，得到如下响应：
+CMGR: "REC READ","+8613426197561",,"06/12/20,19:36:12+00" G,00006,11620284,3955682,2400,9000,120530 OK

请问如何能够得到 G,00006,11620284,3955682,2400,9000,120530 这部分。

+CMGR: "REC READ","+8613426197561",,"06/12/20,19:36:12+00"这是字符串吗？为什么Len("+CMGR: "REC READ","+8613426197561",,"06/12/20,19:36:12+00"") 显示出错？

LEN 是檢測字符串的長度```

+CMGR: "REC READ","+8613426197561",,"06/12/20,19:36:12+00"这是字符串吗？