Path: utzoo!attcan!utgpu!watserv1!watmath!att!pacbell.com!ucsd!usc!zaphod.mps.ohio-state.edu!think.com!barmar From: barmar@think.com (Barry Margolin) Newsgroups: comp.bugs.4bsd Subject: Re: rlogin -8 uses RAW rather than CBREAK mode Message-ID: <1990Dec21.185959.1671@Think.COM> Date: 21 Dec 90 18:59:59 GMT References: <1990Dec21.001643.14510@Think.COM> <88236@lll-winken.LLNL.GOV> Sender: news@Think.COM Organization: Thinking Machines Corporation, Cambridge MA, USA Lines: 55 In article <88236@lll-winken.LLNL.GOV> casey@gauss.llnl.gov (Casey Leedom) writes: > "-8" is used to implement an 8-bit transparent link. The documentation (on a MORE/4.3 system and a Sun) just says 8-bit; it says nothing about transparency. > Allowing START >and STOP character processing would defeat that purpose. I use "-8" to >rlogin over from a terminal server and run a remote X server on a Sun >host for instance. Normally "-8" should be used with out of band or no >flow control. When you start the remote X server, doesn't it put the terminal in raw mode? That will cause rlogind to send the TIOC_NOSTOP command to rlogin, which will cause it to disable the start and stop character processing. At this point you will have an 8-bit, transparent data path to the terminal. Why would the purpose be defeated? Actually, one possibility that has just occurred to me is that some people might rlogin to a non-Unix host that doesn't actually have commands to enable/disable flow control. In fact, I once implemented an rlogin server for such a host. The right thing is for the server to send an immediate TIOC_NOSTOP when the connection is first opened, since it's the one that wants the transparent path. Instead, this was put into the rlogin command by overloading the -8 option. If it must be in rlogin, it would probably be better to have a separate -raw option. > It sounds like you have an application that generally wants to use >8-bits, but doesn't care if some STOP and some START characters are >sucked out of the data stream, and you don't have out of band flow >control capability, and you need some form of flow control. Yes. I noticed this when using SunLink X.25. We have a Sun that is connected to all our dialup modems and an X.25 public network. After prompting for the user name and password it prompts for a host and executes "rlogin -8 "; we use -8 because some of our users have terminals with meta keys that simply turn on the high-order bit, and Emacs recognizes this use. The X.25/X.29 protocol includes a mechanism for the host to tell the PAD to perform XON/XOFF flow control, and I'd like to be able to use that when the user is not in a raw-mode application such as Emacs (single-character round-trip time in X.25 is not great). > Probably your >best bet is to implement a "-cbreak" flag ("-c" for dyed in the wool >single character Unix switch fans) to indicate that while you want LITOUT >and PASS8, you want it to use CBREAK rather than the more intuitive RAW. That's probably what I'll do. I was mostly looking for warnings about possible side-effects of the behavior that I wasn't aware of, and which would be broken by such a mode. -- Barry Margolin, Thinking Machines Corp. barmar@think.com {uunet,harvard}!think!barmar