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Full Discussion: Telnet vs netcat behavior
Top Forums UNIX for Advanced & Expert Users Telnet vs netcat behavior Post 302910336 by ckmehta on Wednesday 23rd of July 2014 04:27:22 PM
Old 07-23-2014
Telnet vs netcat behavior

Currently I run a number of network tests using netcat that checks for an open port on a remote IP-address, using this syntax:
Code:
netcat -v -w 5 -z 107.249.95.5 4488

For some reason, the netcat command above is hanging (although others work fine), but a telnet is showing a valid connection like below:
Code:
%  telnet 107.249.95.5 4488
Trying 107.249.95.5...
Connected to 107.249.95.5.
Escape character is '^]'.
^]

Normally with my other netcat tests, I see an immediate result like this:
aaaa.XXX.com [102.19.5.62] 22 (ssh) open
aaaa.XXX.com [102.19.5.62] 23 (telnet): Connection timed out

The only thing different/interesting about the 107.249.95.5 address is that it is over a VPN to an MQ server.

Any idea why this network test is failing, even though its obviously connectable over telnet. If it matters, I am running this on a Solaris 10 box.

Last edited by ckmehta; 07-23-2014 at 05:32 PM..
 

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ppmtosixel(1)						      General Commands Manual						     ppmtosixel(1)

NAME
ppmtosixel - convert a portable pixmap into DEC sixel format SYNOPSIS
ppmtosixel [-raw] [-margin] [ppmfile] DESCRIPTION
Reads a portable pixmap as input. Produces sixel commands (SIX) as output. The output is formatted for color printing, e.g. for a DEC LJ250 color inkjet printer. If RGB values from the PPM file do not have maxval=100, the RGB values are rescaled. A printer control header and a color assignment table begin the SIX file. Image data is written in a compressed format by default. A printer control footer ends the image file. OPTIONS
-raw If specified, each pixel will be explicitly described in the image file. If -raw is not specified, output will default to com- pressed format in which identical adjacent pixels are replaced by "repeat pixel" commands. A raw file is often an order of magni- tude larger than a compressed file and prints much slower. -margin If -margin is not specified, the image will be start at the left margin (of the window, paper, or whatever). If -margin is speci- fied, a 1.5 inch left margin will offset the image. PRINTING
Generally, sixel files must reach the printer unfiltered. Use the lpr -x option or cat filename > /dev/tty0?. BUGS
Upon rescaling, truncation of the least significant bits of RGB values may result in poor color conversion. If the original PPM maxval was greater than 100, rescaling also reduces the image depth. While the actual RGB values from the ppm file are more or less retained, the color palette of the LJ250 may not match the colors on your screen. This seems to be a printer limitation. SEE ALSO
ppm(5) AUTHOR
Copyright (C) 1991 by Rick Vinci. 26 April 1991 ppmtosixel(1)
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