The telnet standard says that LF should be considered to move the printer to the next line in the same horizontal position and that CR should be considered to move the printer to beginning of the current line, and that...

the sequence "CR LF" must be treated as a single "new line" character and used whenever their combined action is intended

Implying that CR LF is going to be the only newline sequence you will recieve in a telnet stream which is presumably being used here. So there is no need to check for just CR or LF/NL.

Also, note that \r\n is not portable between platforms -- \n and \r are swapped on Macs (because CR is used to terminate lines on Macs, not LF/NL.)