system.serial.readUntil(port, delimiter, includeDelimiter, timeout)
String port - The previously configured serial port to use.
char delimiter - The delimiter to read until.
boolean includeDelimiter - If true, the delimiter will be included in the return value.
int timeout - Optional timeout in milliseconds. Default is 5000. (Since 7.8.0)
String - Returns a String containing all 8-bit ASCII characters read until the delimiter was reached, and including the delimiter if the "includeDelimiter" parameter was true.