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How to set up a remote debug session using a null modem cable
Article ID: 151981 - View products that this article applies to.
This article was previously published under Q151981
This article describes how to set up the debugger on a Windows-based computer by using a null modem cable that is attached to another Windows-based computer.
This section includes the following topics:
Determine the Need for the Kernel DebuggerThe kernel debugger that comes with Windows provides information about the computer that is typically not available without the aid of the debugger. Windows can turn on the kernel debugger from the Windows Start-Up menu (Boot.ini). When you turn on the kernel debugger, Windows debugger can output debugging information to a remote debugger for a remote user to analyze. This is typically done at the request of a Microsoft support professional for analyzing a fatal error in Windows that cannot be diagnosed from the Memory.dmp file or when a Memory.dmp file is not produced.
About Remote DebuggingFor our discussion the target computer is the computer that is being debugged and the host computer is the computer doing the debugging. The process of remote debugging occurs when two computers are connected by the serial communication ports. The target computer and the host computer are running the Windows kernel debuggers, which communicate using a special debug API and protocol. To download the Debugging Tools for Windows, visit the following Microsoft Web site:
Use a Null Modem CableIf you connect the null modem cable to a serial port, the debugger can run at its current top speed of 19200, compared to the speed of 9600 over a modem. This configuration is generally considered more reliable than using a modem for the following reasons:
Change the Attributes on the Boot.ini FileTo set up the target computer, edit Boot.ini in the boot partition, and then add the appropriate debugger options. Use a standard ASCII text editor. The Boot.ini file is hidden in the boot partition directory. The Boot.ini file attributes are hidden, read-only and system. Before you can edit the Boot.ini file, you must change these attributes.
To change the attributes of the Boot.ini file, at the command prompt type attrib -h -r -s c:\boot.ini, and then press Enter. Use Notepad or another text editor to edit the Boot.ini file.
After you edit the file, type attrib +h +r +s c:\boot.ini at the command prompt, and then press ENTER to restore the read-only, hidden, and system file attributes. Alternatively, you can use File Manager instead of a command prompt to change the file attributes. To do so:
Debugger OptionsAfter you open the Boot.ini file on the target computer for editing, you can add any of the following options to configure the debugger environment on the target computer:
Configure the Debugger for the ComputerThere are several options available for configuring the debugger on the target computer. To add any one of the previous options to the Boot.ini file, use the following example.
The following text is a typical Boot.ini. Each entry in the [operating systems] section corresponds to the options that are listed in the boot menu during a typical system startup.
To turn on the debugger use COM1 to perform the following procedure:
[boot loader] timeout=30 default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS [operating systems] multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Windows NT" Version 3.5" multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Windows NT" Version 3.5 [VGA mode]" /BASEVIDEO C:\="MS-DOS"
[boot loader] timeout=30 default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS [operating systems] multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Windows NT" Version 3.5" /debug /debugport=com1 multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Windows NT" Version 3.5 [VGA mode]" /BASEVIDEO C:\="MS-DOS"
Set Up the Null Modem CableA null modem cable is a serial cable that has been configured to allow data to be sent between two serial ports. Typically, you connect a serial port to a serial device. In this case, you must configure the target computer to accept a serial-port-to-serial-port connection. It is important that you use a null modem cable because if you use a typical serial cable the target computer expects a serial device, not another serial port, and you cannot debug the computer.
When you use a null modem to make a direct serial connection between two computers, your cable must be wired as shown in the following tables.
9-Pin NULL Modem Cabling Remote host serial port connector Host system serial port connector Signal 3 2 Transmit Data 2 3 Receive Data 7 8 Request to Send 8 7 Clear to Send 6, 1 4 Data Set Ready and Carrier Detect 5 5 Signal Ground 4 6, 1 Data Terminal Ready 25-Pin NULL Modem Cabling 2 3 Transmit Data 3 2 Receive Data 4 5 Request to Send 5 4 Clear to Send 6 20 Data Set Ready and Carrier Detect 7 7 Signal Ground 20 6 Data Terminal Ready
Configure the Host Computer for a Remote.exe SessionIn this scenario, the host computer is being set up to do a debug of the target computer as if there were a technical support professional sitting at the host computer. Remote.exe runs to permit this debug session to be accessed remotely through a remote access connection.
Remote.exe is a command-line utility that you can use to run command-line programs on remote computers. Remote.exe uses two parts, the server component and the client component. To use Remote.exe, you must first start the server end on the computer that you are debugging from. When you do so, other users can connect to your debugging session by using the client portion of Remote.exe. Remote.exe comes with the Resource Kit. For more details and the command syntax of this utility, see the Resource Kit online help.
The Windows installation CD and the Windows Resource Kit CD is available to achieve this setup.
Additional Information Resources
Article ID: 151981 - Last Review: December 3, 2007 - Revision: 10.3