With EndString = "rnOKrn"

1: Received CR => match for EndString[0], try EndString[1] next;
2: Received LF => match for EndString[1], try EndString[2] next;
3: Received CR => doesn't match EndString[2], try EndString[0] next;
4: Received LF => doesn't match EndString[0], keep looking for a match for EndString[0]