Socket without endlines

[piderman]

Hi,

I'm trying to make a client for the DC protocol using Tcl/Tk. The major problem is that this protocol doesn't send endlines, but rather the | character to end a command.
This poses great problems. For one, 'gets' will always return an empty string, and 'read' will block when reading more characters than are waiting, even when in nonblocking mode.
Secondly I cannot use the 'fileevent readable' command, because the socket doesn't become unreadable as that is done after reading and endline character (so I gather), so the script is executed only once, at the initiation of the 'fileevent'.

How can I solve this?

 

[Bong]

I suppose you have tried fconfigure <socketID> -translation binary?

Bob Rashkin
rrashkin@csc.com

 

[marsd]

Okay, a couple of things.
Fileevent is not waiting on newlines.
Either SIGIO or polling determine when
data is available, depending on how the
socket is fconfigured.

Bong is right on with the fconfigure advice.
You will end up reading the input as raw bytes
and using the binary command you can translate
your input if necessary.

You can also look at pktsrc if you are developing
for *nix. This package adds support for raw packets
in tcl and is not hard to use.

http://home.comcast.net/~maccody/

 

[piderman]

Okay, thanks for the info. I see now I made an error in my program :$. This is the solution I have conjured and it works:

proc readcommand {s} {
   set command ""
   # just need a character other than | :)
   set char c
   while {$char != "|"} {
      set char [read $s 1]
      append command $char
   }
   #process $command
}

set s [socket $host $port]
fconfigure -blocking 0 -buffering none
fileevent $s readable "readcommand $s"

It appears the '-translation binary' is not necessary. Anyway, my manual says that the translation option does exactly that, it translates but commands like 'gets' still need the endline (\n or \r\n etc) to return the input.