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Launching telnet using java program fails with Win 7 OS

Sham Phadtale
Ranch Hand

Joined: Jul 29, 2008
Posts: 75
I have sample program which launches telnet on Windows XP OS.



In Win 07 we need to manually turned on telnet option. I did it. I able to launch telnet from cmd but above java program fail to launch telnet on Win 7.

What I need to do to launch telnet using Java on Win 7?
Brian Burress
Ranch Hand

Joined: Jun 30, 2003
Posts: 122
Is there an exception / stack trace that can be shared?
William Brogden
Author and all-around good cowpoke
Rancher

Joined: Mar 22, 2000
Posts: 12769
    
    5
Where are you consuming std out and std err and providing std in streams? Read the javadocs for java.lang.Process

Bill
Campbell Ritchie
Sheriff

Joined: Oct 13, 2005
Posts: 38334
    
  23
. . . and the classic article which you can find by Googling for Michael Daconta when Runtime.exec() won't.
Sham Phadtale
Ranch Hand

Joined: Jul 29, 2008
Posts: 75
Thanks all for your quick replies.
I read the classic article. I updated the code as given in article as -



I am getting following out put

Execing cmd.exe /C telnet
ERROR>'telnet' is not recognized as an internal or external command,
ERROR>operable program or batch file.
ExitValue: 1

I can run telnet by opening Start--->cmd---->telnet but not through java program.
What I need to do to run telnet from Java program?
John Jai
Bartender

Joined: May 31, 2011
Posts: 1776
You might consider using the Apache Commons Net package. It lists Telnet in the supported protocol. This examples guide can help you start.

Note that while executing telnet you fork a sub-process from the cmd.exe. Try giving the dir command in your code and check if it works first with the cmd.
Sham Phadtale
Ranch Hand

Joined: Jul 29, 2008
Posts: 75
dir works from my Java program, it opens command prompt and shows directories.

I will check Apache Commons Net package.
Rob Spoor
Sheriff

Joined: Oct 27, 2005
Posts: 19670
    
  18

Are you using a 32-bit JVM?

I've tried it on my system as well without Java. I opened CMD from the start menu which will then open a 64-bit CMD window. Telnet works in it. I then opened CMD from Total Commander. Since Total Commander is 32-bit, it launches a 32-bit CMD. Telnet does not work in that. Apparently, on a 64-bit Windows 7 system, telnet only works when launched from a 64-bit application.


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Sham Phadtale
Ranch Hand

Joined: Jul 29, 2008
Posts: 75
Telnet works with CMD but does not work when launch from java program.
John Jai
Bartender

Joined: May 31, 2011
Posts: 1776
I guess Rob tells that telnet does not launch from a 32-bit JVM and only on a 64-bit JVM (in case of Win7 i believe). What is the bit version of the JVM that executes your java program and that invokes the cmd.exe?

Which one listed here is that you have - x86 or x64?
Sham Phadtale
Ranch Hand

Joined: Jul 29, 2008
Posts: 75
OK.. My JVM is 32 bit. I will try by installing 64 bit JVM and check the result.
 
I agree. Here's the link: http://aspose.com/file-tools
 
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