Remove extra carriage return (0D) on socket communications

PhillyR has asked for the wisdom of the Perl Monks concerning the following question:

Update: I've isolated the problem to when the stream gets written to $buf1. I wrote <$lstream1> out and it had just x0As. After $buf1 = <$lstream1> then there were the incorrect x0D x0As. Any recommendations on using this buffer??

I have written a proxy that forwards data it receives to connected clients. It is written in ActivePerl running on a Windows system. When it receives a line feed (0A) character it writes out a carriage return (0D) and a line feed (0A). I need the input unmodified (ie just OA). How do I suppress the OD? I thought using binmode ($fh, ":raw") was supposed to help with this. Any thoughts? Here is the portion that handles receiving the stream and sending to all connected clients...

sub stream1 {
  my ($lstream1) = @_; #socket data comes in on
  my $buf1;            #buffer receiving stream

  if($lstream1->connected) {
    while(defined($buf1=<$lstream1>)) {  #PROBLEM
      foreach my $fn (@stream1_clients) { #all connected clients
        open my $fh, ">&=$fn" or warn $! and die;  #open socket to cli
+ent
        binmode($fh, ":raw");  #thought this solved win/unix problems
        print $fh $buf1;
      }
      $|++
    }
  }
  my $stream_ip = $lstream1->peerhost;
  print "*  Stream 1 [$stream_ip:$stream1_prt] disconnected\n";
  close($lstream1);
}
[download]

Comment on Remove extra carriage return (0D) on socket communications Download Code

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Re: Remove extra carriage return (0D) on socket communications by roboticus (Chancellor) on Nov 11, 2011 at 15:56 UTC
PhillyR: binmode simply tells perl not to change any of the bytes in the stream. If the other side of your pipe is putting in the carriage returns, then binmode isn't going to take them out. If you can use binmode on the other end of the pipe that should solve your problem. If not, you'll have to strip them out. ...roboticus When your only tool is a hammer, all problems look like your thumb.	[reply]
Re: Remove extra carriage return (0D) on socket communications by Marshall (Canon) on Nov 11, 2011 at 23:32 UTC
I'm not sure that what you have is a Windows vs Unix problem. Standard network termination is 0D0A (like how a Windows box likes to do). So even if 2 Unix boxes were talking in a text mode over a socket, the data over the socket would be CRLF terminated instead of the normal LF like to a terminal/local file. So, on the Unix box, print() does different things depending upon whether it is talking to a network connection or a local file on a Unix box. I think you are going to wind up using read() and write() instead of print() if you want absolute control of exactly what is sent over the socket. In that case, you would be taking on the job of figuring out what a "line" is.	[reply]
Re^2: Remove extra carriage return (0D) on socket communications by BrowserUk (Patriarch) on Nov 12, 2011 at 01:01 UTC
I'm not sure that what you have is a Windows vs Unix problem. Agreed. But the simplest solution would probably be to use the `:crlf` IO layer on the socket handle(s). Then print and readline should do the right thing, just as they do for the windows filesystem. With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday' Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice.	[reply] [d/l]
Re: Remove extra carriage return (0D) on socket communications by Anonymous Monk on Nov 11, 2011 at 15:55 UTC
Maybe a dumb question, but did you use binmode on both the input and the output? I only see one open in that code.	[reply]
Re^2: Remove extra carriage return (0D) on socket communications by PhillyR (Acolyte) on Nov 11, 2011 at 16:59 UTC
Not a dumb question. I just added binmode every time I declared a socket or accepted a new socket from a listen socket.... Still get 0D 0A!!	[reply]
Re: Remove extra carriage return (0D) on socket communications by johnny_carlos (Scribe) on Nov 11, 2011 at 16:30 UTC
A bit out of my league, but in searching, open has pragma for output handles: use open OUT => ':bytes'; EDIT: Correct link to documentation	[reply]
Re^2: Remove extra carriage return (0D) on socket communications by PhillyR (Acolyte) on Nov 11, 2011 at 17:06 UTC
I'm looking at this. Not sure I understand how I would use. Something like the following: `open my $fh, ">&=$fn:bytes" or warn $! and die; #open socket to clien +t` [download]	[reply] [d/l]
Re^3: Remove extra carriage return (0D) on socket communications by johnny_carlos (Scribe) on Nov 11, 2011 at 19:09 UTC
PhillyR I'm sorry, my documentation link didn't go to the correct place. This is what I meant It's a pragma, so you'd put it at the top of you code, like "use strict;"	[reply]