Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!rutgers!apple!bionet!agate!ucbvax!GYRE.UMD.EDU!chris
From: chris@GYRE.UMD.EDU (Chris Torek)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: mysterious 0x80... bytes from rlogin servers
Message-ID: <8809291915.AA25643@gyre.umd.edu>
Date: 29 Sep 88 19:15:56 GMT
Sender: usenet@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 23

These bytes are sent as urgent (in 4BSD, `out of band') data, and
are intended to act as control operations.  The bits are defined
as follows:

#define	TIOCPKT_FLUSHREAD	0x01	/* flush packet */
#define	TIOCPKT_FLUSHWRITE	0x02	/* flush packet */
#define	TIOCPKT_STOP		0x04	/* stop output */
#define	TIOCPKT_START		0x08	/* start output */
#define	TIOCPKT_NOSTOP		0x10	/* no more ^S, ^Q */
#define	TIOCPKT_DOSTOP		0x20	/* now do ^S ^Q */
#define	TIOCPKT_WINDOW		0x80	/* can use new window size protocol */

The window size protocol consists of having the rlogin client send window
size changes as the sequence 0xff, 0xff, 's', 's', <rows>, <columns>,
<x-pixels>, <y-pixels>, where <> quantities are two bytes in network
(BigEndian) order.

There is (as yet) no way to send 0xff bytes when using the window size
protocol, but obviously one of (0xff <something other than 0xff>) or
(0xff 0xff <something other than `ss'>) will be used.  I favour 0xff 0x00
myself...

Chris