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Full Discussion: "Phantom character" in Socket (RESOLVED)
Top Forums UNIX for Advanced & Expert Users "Phantom character" in Socket (RESOLVED) Post 302332247 by trutoman on Thursday 9th of July 2009 09:18:12 AM
Old 07-09-2009
"Phantom character" in Socket (RESOLVED)
Hi everyone:

I have built a tcl script, this script communicate with an ADA program trough a socket, sending binary data, the sender proc is this one:

The code where im sending info is here:
Code:
proc p_send_data { DATA } {
  global connection
  puts "Sending trough $connection..."
 
  # This is just the string of bytes im sending
  binary scan $DATA H22 hexa
  puts "IM SENDING THIS ------>  $hexa"

  # Put it trough socket
  puts -nonewline "$connection" $DATA
  flush $connection
  }

It usually works fine, but with some values of DATA, socket, a little demon or something is adding a byte to my string !!

The output of program "IM SENDING THIS -----> 0109450900018813bc0400"

Like you can see this line is printed just before puts data in socket.

The "tcpdump" capture ----------------------------------> 010945090001c28813bc0400

The bytes are the same excepts that c2 insertion.

With strace i can see how system writes in socket this:

Code:
write(1, "IM SENDING THIS ------>  010945090001"..., 44IM SENDING THIS ------>  0109450900018813bc0400) = 44
sendto(4, "\1\tE\t\0\1\302\210\23\302\274\4\0001212", 17, 0, NULL, 0) = 17

Sometimes with different values of DATA this byte "c2" appears......always in the same position !! . After looking info trough internet, iknow that c2 is 194 in decimal and it doesn't look like a dangerous character like "\00" "\7f" could be.

Perhaps an error in c libraries of sockets??

This is my system : Linux 2.6.9-67
TCLInterpreter : 8.4

Plz Help me . THX!!

---------- Post updated 09-07-09 at 03:18 PM ---------- Previous update was 08-07-09 at 07:01 PM ----------

Nobody response.

I have fixed it !!!! exactly 20 hours after.

Par default a socket connection its created with "-encoding = utf-8" . But i was sending binary data, so sometimes (when my binary bytes matched up with a ascii code) it interpret that like some ascii char and the socket translated automatically to ascii code.
So the solution is to configure socket with "-encoding = binary".in tcl.
"fconfigure connection -encoding binary"

it was quite easy ....... like ever.
 

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LEARN ABOUT SUSE

source

source(n)						       Tcl Built-In Commands							 source(n)

__________________________________________________________________________________________________________________________________________________

NAME

       source - Evaluate a file or resource as a Tcl script

SYNOPSIS

       source fileName

       source -encoding encodingName fileName													   |
_________________________________________________________________

DESCRIPTION

       This  command takes the contents of the specified file or resource and passes it to the Tcl interpreter as a text script.  The return value
       from source is the return value of the last command executed in the script.  If an error occurs in evaluating the contents  of  the  script
       then  the source command will return that error.  If a return command is invoked from within the script then the remainder of the file will
       be skipped and the source command will return normally with the result from the return command.

       The end-of-file character for files is "32" (^Z) for all platforms.  The source command will  read  files  up  to  this  character.   This
       restriction  does  not  exist for the read or gets commands, allowing for files containing code and data segments (scripted documents).	If
       you require a "^Z" in code for string comparison, you can use "32" or "u001a", which will be safely substituted by the  Tcl  interpreter
       into "^Z".

       The  -encoding  option  is  used  to specify the encoding of the data stored in fileName.  When the -encoding option is omitted, the system |
       encoding is assumed.

EXAMPLE

       Run the script in the file foo.tcl and then the script in the file bar.tcl:
	      source foo.tcl
	      source bar.tcl
       Alternatively:
	      foreach scriptFile {foo.tcl bar.tcl} {
		 source $scriptFile
	      }

SEE ALSO

       file(n), cd(n), encoding(n), info(n)

KEYWORDS

       file, script

Tcl																	 source(n)
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