Rclient.exe Fails After 9 Connections

• Microsoft Windows NT Server versions 3.51 and 4.0

SYMPTOMS

If you have nine connections of Rclient.exe running on the same computer then attempt to add a tenth (or more), the tenth connection will appear to stop responding. The first nine connections keep on working normally. Killing or exiting from one of the nine working connections will free up resources that allow the tenth connection to start working normally.

CAUSE

Rclient.exe is the client of the Remote Console utility, which allows the user to remotely take control of a CMD console session and is included in the Windows NT 4.0 Resource Kit. Remote Console is composed of a service, the server, and a client. (For more information on Remote Console, please refer to the resource kit help files.)

The Remote Console client, Rclient.exe, makes intensive use of completion I/O ports. By default, it uses three worker threads: one to send the data to the server and two to read the data from the server. As Remote Console works entirely asynchronously, the two read operations are in a pending state most of the time, and all the redirector resources are consumed.

RESOLUTION

Modify the number of redirector worker threads at the client side by editing the registry.

WARNING: Using Registry Editor incorrectly can cause serious, system-wide problems that may require you to reinstall Windows NT to correct them. Microsoft cannot guarantee that any problems resulting from the use of Registry Editor can be solved. Use this tool at your own risk.

Modify the following value under the registry key HKEY_LOCAL_MACHINE\SYSTEM\CCS\Services\LanmanWorkstation\Parameters (CCS is for CurrentControlSet):

ValueName = MaxThreads REG_DWORD

Default   = 17

This will enable up to 49 simultaneous instances of Rclient on a single computer. Notice that going above the limit also requires modification of the server parameters on the server.

STATUS

Microsoft has confirmed this to be a problem in Microsoft Windows NT versions 3.51 and 4.0. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.