Connect and fetch data every X minutes

Projects Networking, Protocols, and Devices
2 
    char c = client.read();
    //Serial.print(c);
    readString = c;
    int d1 = readString.indexOf('<');
    int d2 = readString.indexOf('>');
    readString1 = (readString.substring(d1+1,d2));

If c is <, it can't also be >. If it is >, it can't also be >. So, there are 3 possibilities:

  1. d1 could be -1 because c is >.
  2. d2 could be -1 because c is <.
  3. d1 and d2 are both -1 because c is something other than < or >.

In any case, the inputs to String::substring() are always invalid.