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Path: utzoo!mnetor!seismo!ut-sally!husc6!cmcl2!brl-adm!adm!scott@gateway.mitre.ORG
From: scott@gateway.mitre.ORG
Newsgroups: comp.unix.wizards
Subject: Telnet flow control
Message-ID: <7758@brl-adm.ARPA>
Date: Tue, 9-Jun-87 07:33:55 EDT
Article-I.D.: brl-adm.7758
Posted: Tue Jun  9 07:33:55 1987
Date-Received: Fri, 12-Jun-87 01:53:48 EDT
Sender: news@brl-adm.ARPA
Lines: 66


About every couple of months some complains about loosing characters
over telnet.  Well, telnet runs over TCP and TCP does NOT drop characters.
The problem is that the distributed telnet turns off local flow control
(UCB telnet that is, I can't speak for other telnets).  Here is a modified
``mode'' function taken from a 4.2bsd telnet that reinstates local
flow control.  I have heard that the 4.3 telnet is similar but I haven't
had the need to change it yet.

		John <scott@gateway.mitre.org>

	As always Mr. Scott, should you or any of your IM force be
	caught or killed, the secretary will disavow any knowledge
	of the operation.  You're on your own John. Good Luck!


struct	tchars notc =	{ -1, -1, -1, -1, -1, -1 };
struct	ltchars noltc =	{ -1, -1, -1, -1, -1, -1 };

mode(f)
	register int f;
{
	static int prevmode = 0;
	struct tchars *tc;
	struct ltchars *ltc;
	struct sgttyb sb;
	int onoff, old;

	if (prevmode == f)
		return (f);
	old = prevmode;
	prevmode = f;
	sb = ottyb;
	switch (f) {

	case 0:
		onoff = 0;
		tc = &otc;
		ltc = &oltc;
		break;

	case 1:
	case 2:
		sb.sg_flags |= CBREAK;
		if (f == 1)
			sb.sg_flags &= ~(ECHO|CRMOD);
		else
			sb.sg_flags |= ECHO|CRMOD;
		sb.sg_erase = sb.sg_kill = -1;
		tc = &notc;
		tc->t_stopc = otc.t_stopc;		/* hacks to allow */
		tc->t_startc = otc.t_startc;		/* flow control */
		ltc = &noltc;
		onoff = 1;
		break;

	default:
		return;
	}
	ioctl(fileno(stdin), TIOCSLTC, (char *)ltc);
	ioctl(fileno(stdin), TIOCSETC, (char *)tc);
	ioctl(fileno(stdin), TIOCSETP, (char *)&sb);
	ioctl(fileno(stdin), FIONBIO, &onoff);
	ioctl(fileno(stdout), FIONBIO, &onoff);
	return (old);
}